Income Taxes - Narratives (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			6 Months Ended
	Dec. 31, 2017	Jun. 30, 2018	Dec. 31, 2017	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Operating Loss Carryforwards
Effective rate for continuing operations (percent)		39.50%		27.90%	20.40%	27.90%
Income tax expense		$ 23,189		$ 17,703	$ 19,164	$ 19,955
Effective income tax expense (benefit) related to share based compensation		3,400		(1,000)	(5,300)	(1,300)
Increase for tax positions taken during the current period		2,700			2,700
Tax benefit from the exercise of stock options		300			1,500
Interest expense from uncertain tax positions		400			600
Effective income tax rate reconciliation, revenue basis adjustments					7,100
Unrecognized tax benefits	$ 13,300	13,900	$ 13,300		13,900
Tax Cuts And Jobs Act, additional income tax expense impacting deferred tax assets	21,100
Tax Cuts and Jobs Act, incomplete accounting, transition tax for accumulated foreign earnings, income tax	$ 11,300
Foreign source dividends			$ 65,800
Continuing operations
Operating Loss Carryforwards
Income tax expense		$ 23,200		$ 17,700	$ 19,200	$ 20,000