Quarterly report pursuant to Section 13 or 15(d)

Senior Credit Facility (Details)

v3.8.0.1
Senior Credit Facility (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2017
Sep. 30, 2016
Sep. 29, 2017
Feb. 04, 2015
Debt Instrument [Line Items]          
Line of Credit Facility Term, In Years       5  
Credit facility amount       $ 250,000 $ 275,000
Additional borrowing capacity of credit facility       100,000  
Base reference rate of credit facilities   LIBOR      
Interest rate spread above LIBOR as of reporting period (in hundredths)   1.00%      
Proceeds from senior credit facility   $ 55,000 $ 0    
Letters of Credit Outstanding, Amount $ 8,677 8,677      
Available borrowing capacity 100,823 100,823      
Letter of Credit [Member]          
Debt Instrument [Line Items]          
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases       30,000  
Swing line loan [Member]          
Debt Instrument [Line Items]          
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases       $ 30,000  
Revolving Credit Facility [Member]          
Debt Instrument [Line Items]          
Credit facility amount         150,000
Line of Credit Facility, Current Borrowing Capacity 150,000 $ 150,000      
Debt Instrument, Basis Spread on Variable Rate, Minimum       0.30%  
Debt Instrument, Basis Spread on Variable Rate, Maximum       0.80%  
Proceeds from senior credit facility $ 40,500        
Line of Credit Facility, Interest Rate at Period End 2.60% 2.60%      
Federal funds [Member]          
Debt Instrument [Line Items]          
Interest rate spread above LIBOR as of reporting period (in hundredths)   0.50%      
Term loan [Member]          
Debt Instrument [Line Items]          
Credit facility amount         $ 125,000