Credit Agreement (Details) - USD ($) $ in Thousands	Feb. 14, 2018	Dec. 30, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Borrowings under revolving credit facility		$ 24,500	$ 0
March 2017 Amendment [Member]
Line of Credit Facility [Line Items]
Current borrowing capacity		153,000
Borrowings under revolving credit facility		25,000
Letters of Credit Outstanding, Amount		3,000
Line of Credit Facility, Remaining Borrowing Capacity		$ 125,000
Line of Credit Facility, Interest Rate at Period End		3.10%
Subsequent Event [Member] | February 2018 Amendment [Member]
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 300,000
Potential borrowing capacity, with accordion feature	$ 450,000
Line of Credit Facility, Expiration Date	Feb. 14, 2023