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
Mar. 31, 2018
Mar. 31, 2017
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 $ 0 $ 13,000    
Letters of Credit Outstanding, Amount 7,932      
Available borrowing capacity 101,568      
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  
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 3.60%      
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