| Accounting Policies (Details)$ / shares in Units, $ in Thousands
 | 3 Months Ended | 12 Months Ended |  |  | 
| Dec. 31, 2018  USD ($)  Days  $ / shares | Sep. 30, 2018  USD ($)  $ / shares | Jun. 30, 2018  USD ($)  $ / shares | Mar. 31, 2018  USD ($)  $ / shares | Dec. 31, 2017  USD ($)  $ / shares | Sep. 30, 2017  USD ($)  $ / shares | Jun. 30, 2017  USD ($)  $ / shares | Mar. 31, 2017  USD ($)  $ / shares | Dec. 31, 2018  USD ($)  Days  $ / shares | Dec. 31, 2017  USD ($)  $ / shares | Dec. 31, 2016  USD ($)  $ / shares | Jan. 01, 2019  USD ($) | Dec. 31, 2015  USD ($) | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue | $ 356,561 | $ 331,375 | $ 330,343 | $ 302,608 | $ 325,136 | $ 298,289 | $ 283,876 | $ 262,046 | $ 1,320,886 | $ 1,169,346 | $ 1,030,210 |  |  | 
| Accounts Receivable, Net, Current | $ 156,359 |  |  |  | 147,948 |  |  |  | $ 156,359 | 147,948 |  |  |  | 
| Number of principal reporting segments |  |  |  |  |  |  |  |  | 4 |  |  |  |  | 
| Undistributed Earnings (Loss) Allocated to Participating Securities, Basic |  |  |  |  |  |  |  |  | $ 881 | 700 | 210 |  |  | 
| Amount Reclassified from Current Deferred Tax Asset to Non-current Deferred Tax Liability |  |  |  |  |  |  |  |  |  |  |  |  | $ (558) | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Minimum number of days past due for receivable reserve | Days | 90 |  |  |  |  |  |  |  | 90 |  |  |  |  | 
| Average monthly revenue adjustments |  |  |  |  |  |  |  |  | $ 302 |  |  |  |  | 
| Average monthly revenue |  |  |  |  |  |  |  |  | $ 110,074 |  |  |  |  | 
| Average monthly revenue adjustments as a percentage of monthly revenue | 0.30% |  |  |  |  |  |  |  | 0.30% |  |  |  |  | 
| Number of days in revenue adjustment reserve, minimum | Days |  |  |  |  |  |  |  |  | 35 |  |  |  |  | 
| Number of days in revenue adjustment reserve, maximum | Days |  |  |  |  |  |  |  |  | 85 |  |  |  |  | 
| Self insurance limit on individual vehicle and general claims |  |  |  |  |  |  |  |  | $ 7,500 |  |  |  |  | 
| Insurance Settlements Receivable | $ 28,520 |  |  |  | 8,133 |  |  |  | $ 28,520 | 8,133 |  |  |  | 
| Accounting Policies, Cash and Cash Equivalents [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Maximum term for liquid investments to be considered cash equivalents, in months |  |  |  |  |  |  |  |  | 3 months |  |  |  |  | 
| Accounting Policies, Property and Equipment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Depreciation |  |  |  |  |  |  |  |  | $ 33,044 | 30,862 | 28,088 |  |  | 
| Accounting Policies, Software Development [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Capitalized software development costs | 21,492 |  |  |  | 19,567 |  |  |  | 21,492 | 19,567 |  |  |  | 
| Capitalized computer software, accumulated amortization | 15,611 |  |  |  | 13,706 |  |  |  | 15,611 | 13,706 |  |  |  | 
| Capitalized Computer Software, Amortization |  |  |  |  |  |  |  |  | 1,905 | 1,816 | 1,658 |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Deferred Tax Liabilities, Net, Noncurrent | 37,174 |  |  |  | 29,080 |  |  |  | 37,174 | 29,080 |  |  |  | 
| Retained Earnings (Accumulated Deficit) | 342,663 |  |  |  | 337,058 |  |  |  | 342,663 | 337,058 |  |  |  | 
| Costs and Expenses |  |  |  |  |  |  |  |  | 1,198,855 | 1,060,589 | 970,507 |  |  | 
| Operating Income (Loss) | 35,047 | 29,879 | 32,870 | 24,235 | 27,843 | 27,176 | 29,996 | 23,743 | 122,031 | 108,757 | 59,703 |  |  | 
| Income Tax Expense (Benefit) |  |  |  |  |  |  |  |  | 28,195 | 20,282 | 30,605 |  |  | 
| Net income (loss) | $ 27,684 | $ 22,329 | $ 24,298 | $ 17,741 | $ 34,681 | $ 18,328 | $ 19,666 | $ 14,581 | $ 92,051 | $ 87,255 | $ 27,505 |  |  | 
| Diluted net income per share | $ / shares | $ 0.95 | $ 0.76 | $ 0.82 | $ 0.60 | $ 1.16 | $ 0.61 | $ 0.65 | $ 0.48 | $ 3.12 | $ 2.89 | $ 0.90 |  |  | 
| Self insurance retention liability |  |  |  |  |  |  |  |  | $ 3,000 |  |  |  |  | 
| Self-insurance retention Workers' compensation |  |  |  |  |  |  |  |  | $ 350 |  |  |  |  | 
| Software and Software Development Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Property and Equipment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property and equipment, useful life |  |  |  |  |  |  |  |  | 5 years |  |  |  |  | 
| Capitalized software future estimated amortization expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| 2019 | $ 1,605 |  |  |  |  |  |  |  | $ 1,605 |  |  |  |  | 
| 2020 | 1,263 |  |  |  |  |  |  |  | 1,263 |  |  |  |  | 
| 2021 | 932 |  |  |  |  |  |  |  | 932 |  |  |  |  | 
| 2022 | 653 |  |  |  |  |  |  |  | 653 |  |  |  |  | 
| 2023 | 382 |  |  |  |  |  |  |  | 382 |  |  |  |  | 
| Total | $ 4,835 |  |  |  |  |  |  |  | $ 4,835 |  |  |  |  | 
| Stock Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Period from grant date of stock options to expiration (in years) |  |  |  |  |  |  |  |  | 7 years |  |  |  |  | 
| Share-based awards, vesting period |  |  |  |  |  |  |  |  | 3 years |  |  |  |  | 
| Expected dividend yield (in hundredths) |  |  |  |  |  |  |  |  | 1.10% | 1.30% | 1.00% |  |  | 
| Expected stock price volatility |  |  |  |  |  |  |  |  | 24.40% | 28.50% | 28.90% |  |  | 
| Weighted average risk-free interest rate |  |  |  |  |  |  |  |  | 2.70% | 2.00% | 1.30% |  |  | 
| Expected life of options (in years) |  |  |  |  |  |  |  |  | 6 years 1 month 11 days | 5 years 10 months 11 days | 5 years 9 months 11 days |  |  | 
| Key Employee Performance Share Based Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Share-based awards, vesting period |  |  |  |  |  |  |  |  | 3 years |  |  |  |  | 
| Expected stock price volatility |  |  |  |  |  |  |  |  | 24.30% | 24.70% | 22.30% |  |  | 
| Weighted average risk-free interest rate |  |  |  |  |  |  |  |  | 2.20% | 1.40% | 0.80% |  |  | 
| Employee Stock Purchase Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Percentage of share price for shares issued under the ESPP (in hundredths) |  |  |  |  |  |  |  |  | 90.00% |  |  |  |  | 
| Purchase Period for Employee Stock Purchase Plan |  |  |  |  |  |  |  |  | 6 months |  |  |  |  | 
| Number of large lump sum contributions related to ESPP stock purchases | 2 |  |  |  |  |  |  |  | 2 |  |  |  |  | 
| Expedited LTL [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  | $ 740,332 | $ 652,304 | $ 593,472 |  |  | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Reserve percentage for past due accounts receivable | 50.00% |  |  |  |  |  |  |  | 50.00% |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  | $ 96,385 | 87,969 | 83,142 |  |  | 
| Intermodal [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  | $ 200,750 | 154,446 | 105,504 |  |  | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Reserve percentage for past due accounts receivable | 10.00% |  |  |  |  |  |  |  | 10.00% |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  | $ 23,266 | 12,963 | 11,060 |  |  | 
| Self insurance retention liability |  |  |  |  |  |  |  |  | 50 |  |  |  |  | 
| Pool Distribution [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  | $ 193,690 | 168,194 | 151,245 |  |  | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Reserve percentage for past due accounts receivable | 25.00% |  |  |  |  |  |  |  | 25.00% |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  | $ 5,870 | 6,378 | 3,633 |  |  | 
| Truckload Premium Services [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  | $ 186,114 | 194,402 | 179,989 |  |  | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Reserve percentage for past due accounts receivable | 50.00% |  |  |  |  |  |  |  | 50.00% |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  | $ 5,055 | 3,215 | (35,409) |  |  | 
| Intersegment Eliminations [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  | $ (8,545) | (1,768) | (2,723) |  |  | 
| Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Lease, Right-of-Use Asset |  |  |  |  |  |  |  |  |  |  |  | $ 130,000 |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Lease, Liability |  |  |  |  |  |  |  |  |  |  |  | 130,000 |  | 
| Minimum [Member] | Building [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Property and Equipment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property and equipment, useful life |  |  |  |  |  |  |  |  | 30 years |  |  |  |  | 
| Minimum [Member] | Equipment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Property and Equipment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property and equipment, useful life |  |  |  |  |  |  |  |  | 3 years |  |  |  |  | 
| Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Lease, Right-of-Use Asset |  |  |  |  |  |  |  |  |  |  |  | 150,000 |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating Lease, Liability |  |  |  |  |  |  |  |  |  |  |  | $ 150,000 |  | 
| Maximum [Member] | Building [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Property and Equipment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property and equipment, useful life |  |  |  |  |  |  |  |  | 40 years |  |  |  |  | 
| Maximum [Member] | Equipment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Property and Equipment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Property and equipment, useful life |  |  |  |  |  |  |  |  | 10 years |  |  |  |  | 
| Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 1,169,346 | 1,030,210 |  |  | 
| Accounts Receivable, Net, Current |  |  |  |  | $ 147,948 |  |  |  |  | 147,948 |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounts Payable |  |  |  |  | 30,723 |  |  |  |  | 30,723 |  |  |  | 
| Deferred Tax Liabilities, Net, Noncurrent |  |  |  |  | 29,080 |  |  |  |  | 29,080 |  |  |  | 
| Retained Earnings (Accumulated Deficit) |  |  |  |  | 337,058 |  |  |  |  | 337,058 |  |  |  | 
| Costs and Expenses |  |  |  |  |  |  |  |  |  | 1,060,589 | 970,507 |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  |  | 108,757 | 59,703 |  |  | 
| Income Tax Expense (Benefit) |  |  |  |  |  |  |  |  |  | 20,282 | 30,605 |  |  | 
| Net income (loss) |  |  |  |  |  |  |  |  |  | $ 87,255 | $ 27,505 |  |  | 
| Diluted net income per share | $ / shares |  |  |  |  |  |  |  |  |  | $ 2.89 | $ 0.90 |  |  | 
| Adjustments for New Accounting Pronouncement [Member] | Expedited LTL [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | $ 655,838 | $ 596,539 |  |  | 
| Adjustments for New Accounting Pronouncement [Member] | Intermodal [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 154,684 | 105,664 |  |  | 
| Adjustments for New Accounting Pronouncement [Member] | Pool Distribution [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 168,483 | 151,852 |  |  | 
| Adjustments for New Accounting Pronouncement [Member] | Truckload Premium Services [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 201,752 | 181,007 |  |  | 
| Adjustments for New Accounting Pronouncement [Member] | Intersegment Eliminations [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | (11,411) | (4,852) |  |  | 
| Restatement Adjustment [Member] | Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 68,530 | 47,680 |  |  | 
| Accounts Receivable, Net, Current |  |  |  |  | 4,907 |  |  |  |  | 4,907 |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounts Payable |  |  |  |  | 6,019 |  |  |  |  | 6,019 |  |  |  | 
| Deferred Tax Liabilities, Net, Noncurrent |  |  |  |  | (323) |  |  |  |  | (323) |  |  |  | 
| Retained Earnings (Accumulated Deficit) |  |  |  |  | (790) |  |  |  |  | (790) |  |  |  | 
| Costs and Expenses |  |  |  |  |  |  |  |  |  | 68,445 | 47,956 |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  |  | 85 | (276) |  |  | 
| Income Tax Expense (Benefit) |  |  |  |  |  |  |  |  |  | 151 | (111) |  |  | 
| Net income (loss) |  |  |  |  |  |  |  |  |  | (66) | (165) |  |  | 
| Restatement Adjustment [Member] | Adjustments for New Accounting Pronouncement [Member] | Expedited LTL [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 36,059 | 25,761 |  |  | 
| Restatement Adjustment [Member] | Adjustments for New Accounting Pronouncement [Member] | Intermodal [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 5,777 | 1,993 |  |  | 
| Restatement Adjustment [Member] | Adjustments for New Accounting Pronouncement [Member] | Pool Distribution [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 4,262 | 3,191 |  |  | 
| Restatement Adjustment [Member] | Adjustments for New Accounting Pronouncement [Member] | Truckload Premium Services [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 22,432 | 16,735 |  |  | 
| Previously Reported [Member] | Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 1,100,816 | 982,530 |  |  | 
| Accounts Receivable, Net, Current |  |  |  |  | 143,041 |  |  |  |  | 143,041 |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounts Payable |  |  |  |  | 24,704 |  |  |  |  | 24,704 |  |  |  | 
| Deferred Tax Liabilities, Net, Noncurrent |  |  |  |  | 29,403 |  |  |  |  | 29,403 |  |  |  | 
| Retained Earnings (Accumulated Deficit) |  |  |  |  | $ 337,848 |  |  |  |  | 337,848 |  |  |  | 
| Costs and Expenses |  |  |  |  |  |  |  |  |  | 992,144 | 922,551 |  |  | 
| Operating Income (Loss) |  |  |  |  |  |  |  |  |  | 108,672 | 59,979 |  |  | 
| Income Tax Expense (Benefit) |  |  |  |  |  |  |  |  |  | 20,131 | 30,716 |  |  | 
| Net income (loss) |  |  |  |  |  |  |  |  |  | $ 87,321 | $ 27,670 |  |  | 
| Diluted net income per share | $ / shares |  |  |  |  |  |  |  |  |  | $ 2.89 | $ 0.90 |  |  | 
| Previously Reported [Member] | Adjustments for New Accounting Pronouncement [Member] | Expedited LTL [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | $ 619,779 | $ 570,778 |  |  | 
| Previously Reported [Member] | Adjustments for New Accounting Pronouncement [Member] | Intermodal [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 148,907 | 103,671 |  |  | 
| Previously Reported [Member] | Adjustments for New Accounting Pronouncement [Member] | Pool Distribution [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 164,221 | 148,661 |  |  | 
| Previously Reported [Member] | Adjustments for New Accounting Pronouncement [Member] | Truckload Premium Services [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | 179,320 | 164,272 |  |  | 
| Previously Reported [Member] | Adjustments for New Accounting Pronouncement [Member] | Intersegment Eliminations [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Operating revenue |  |  |  |  |  |  |  |  |  | $ (11,411) | $ (4,852) |  |  | 
| Aggregate deductible for claims between $3,000 and $5,000 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self insurance retention liability additional deductible |  |  |  |  |  |  |  |  | $ 6,000 |  |  |  |  | 
| Aggregate deductible for claims between $3,000 and $5,000 [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self insurance retention liability additonal deductible applicable range |  |  |  |  |  |  |  |  | 3,000 |  |  |  |  | 
| Aggregate deductible for claims between $3,000 and $5,000 [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self insurance retention liability additonal deductible applicable range |  |  |  |  |  |  |  |  | 5,000 |  |  |  |  | 
| Aggregate deductible for claims between $5,000 and $10,000 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self insurance retention liability additional deductible |  |  |  |  |  |  |  |  | 2,500 |  |  |  |  | 
| Aggregate deductible for claims between $5,000 and $10,000 [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self insurance retention liability additonal deductible applicable range |  |  |  |  |  |  |  |  | 5,000 |  |  |  |  | 
| Aggregate deductible for claims between $5,000 and $10,000 [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self insurance retention liability additonal deductible applicable range |  |  |  |  |  |  |  |  | 10,000 |  |  |  |  | 
| Truckload Premium Services [Member] | Aggregate deductible for claims between $0 and $5,000 [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Liability insurance coverage |  |  |  |  |  |  |  |  | 0 |  |  |  |  | 
| Truckload Premium Services [Member] | Aggregate deductible for claims between $0 and $5,000 [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Use of Estimates [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Liability insurance coverage |  |  |  |  |  |  |  |  | 5,000 |  |  |  |  | 
| State of Ohio [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Accounting Policies, Share-based Payments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  | 
| Self-insurance retention Workers' compensation |  |  |  |  |  |  |  |  | $ 500 |  |  |  |  |