Annual report pursuant to Section 13 and 15(d)

Accounting Policies (Details)

v3.6.0.2
Accounting Policies (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
USD ($)
Days
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Accounting Policies [Line Items]      
Number of principal reporting segments 4 3  
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic $ (212) $ (369) $ (404)
Accounting Policies, Use of Estimates [Abstract]      
Minimum number of days past due for receivable reserve | Days 90    
Average monthly revenue adjustments $ 168    
Average monthly revenue $ 81,878    
Average monthly revenue adjustments as a percentage of monthly revenue 0.20%    
Number of days in revenue adjustment reserve, minimum | Days 35    
Number of days in revenue adjustment reserve, maximum | Days 65    
Self insurance limit on individual vehicle and general claims $ 750    
Self insurance limit on workers' compensation claims and health insurance claims 250    
Self Insurance limit on Ohio workers' compensation and health insurance claims 500    
Insurance Settlements Receivable $ 6,711    
Accounting Policies, Cash and Cash Equivalents [Abstract]      
Maximum term for liquid investments to be considered cash equivalents, in months 3    
Accounting Policies, Property and Equipment [Abstract]      
Depreciation $ 28,088 26,252 22,616
Accounting Policies, Software Development [Abstract]      
Capitalized software development costs 16,268 14,866  
Capitalized computer software, accumulated amortization 10,716 10,584  
Capitalized Computer Software, Amortization $ 1,658 $ 1,526 $ 1,464
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      
2017 $ 1,719    
2018 1,400    
2019 1,142    
2020 849    
2021 368    
Total $ 5,478    
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    
Black-Scholes option pricing model assumptions [Abstract]      
Expected dividend yield (in hundredths) 1.00% 1.00% 1.20%
Expected stock price volatility 28.90% 33.30% 38.50%
Weighted average risk-free interest rate 1.30% 1.60% 1.60%
Expected life of options (in years) 5 years 9 months 11 days 5 years 10 months 11 days 5 years 3 months 12 days
Key Employee Performance Share Based Plan [Member]      
Accounting Policies, Share-based Payments [Abstract]      
Share-based awards, vesting period 3 years    
Black-Scholes option pricing model assumptions [Abstract]      
Expected stock price volatility 22.30% 23.50% 32.50%
Weighted average risk-free interest rate 0.80% 1.00% 0.70%
Employee Stock Purchase Plan [Member]      
Black-Scholes option pricing model assumptions [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    
Expedited LTL [Member]      
Accounting Policies, Use of Estimates [Abstract]      
Reserve percentage for past due accounts receivable 50.00%    
Intermodal [Member]      
Accounting Policies, Use of Estimates [Abstract]      
Reserve percentage for past due accounts receivable 10.00%    
Pool Distribution [Member]      
Accounting Policies, Use of Estimates [Abstract]      
Reserve percentage for past due accounts receivable 25.00%    
Truckload Premium Services [Member]      
Accounting Policies, Use of Estimates [Abstract]      
Reserve percentage for past due accounts receivable 50.00%    
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] | 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