Quarterly report pursuant to Section 13 or 15(d)

Senior Credit Facility (Details)

v3.10.0.1
Senior Credit Facility (Details) - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 29, 2017
Debt Instrument [Line Items]      
Proceeds from senior credit facility $ 0 $ 55,000  
Revolving Credit Facility [Member]      
Debt Instrument [Line Items]      
Line of Credit Facility Term, In Years     5
Line of Credit Facility, Current Borrowing Capacity     $ 150,000
Additional borrowing capacity of credit facility     100,000
Credit facility amount     $ 250,000
Base reference rate of credit facilities LIBOR    
Interest rate spread above LIBOR as of reporting period (in hundredths) 1.00%    
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    
Available borrowing capacity $ 98,377    
Line of Credit Facility, Interest Rate at Period End 3.60%    
Letter of Credit [Member]      
Debt Instrument [Line Items]      
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases     $ 30,000
Letters of Credit Outstanding, Amount $ 11,123    
Swing line loan [Member]      
Debt Instrument [Line Items]      
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases     $ 30,000
Federal funds [Member]      
Debt Instrument [Line Items]      
Interest rate spread above LIBOR as of reporting period (in hundredths) 0.50%