Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Apr. 01, 2018	Dec. 31, 2017	Apr. 02, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 2,393		$ 7,535
Effective tax rate	30.00%		32.00%
Additional income tax expense		$ 48,300
Provisional amounts related to remeasurement of certain deferred tax assets and liabilities				$ 26,600
Provisional amount related to one-time transition tax on mandatory deemed repatriation of foreign earnings				$ 21,700
Possible reduction in liabilities for uncertain tax positions	$ 900