Comprehensive Income - Changes In Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Apr. 01, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 650,694	$ 672,909
Other comprehensive income, net of tax
Unrealized gain on cash flow hedging activities, net of income tax of $1,148	3,320
Other comprehensive income (loss)	3,320	(784)
Ending Balance	648,483	650,694
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(784)
Other comprehensive income, net of tax
Unrealized gain on cash flow hedging activities, net of income tax of $1,148	3,320
Other comprehensive income (loss)	3,320
Ending Balance	$ 2,536	$ (784)