Income Taxes Income Taxes - Tax Act (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jul. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017	Dec. 31, 2017
Income Taxes [Line Items]
(Benefit) provision for income taxes		$ (5,124)	$ 2,988	$ (3,199)	$ 20,992
Deferred income tax expense				$ (264)	1,686
Adjustments for new accounting pronouncement [Member]
Income Taxes [Line Items]
(Benefit) provision for income taxes			$ (315)		$ 2,674
Tax Act [Member] | Provisional [Member]
Income Taxes [Line Items]
(Benefit) provision for income taxes						$ 7,500
Effective of change in enacted tax rate, amount						100
Repatriation of foreign earnings, amount						200
Tax Act [Member] | Provisional [Member] | Deferred tax liabilities [Member]
Income Taxes [Line Items]
Effective of change in enacted tax rate, amount						3,900
Tax Act [Member] | Provisional [Member] | Deferred tax assets [Member]
Income Taxes [Line Items]
Deferred income tax expense						800
Tax Act [Member] | Provisional [Member] | Adjustments for new accounting pronouncement [Member]
Income Taxes [Line Items]
Deferred income tax expense						5,600
Tax Act [Member] | Provisional [Member] | U.S. [Member]
Income Taxes [Line Items]
Deferred income tax expense	[1]					1,600
Change in deferred tax assets valuation allowance						$ 4,700

[1] Includes $4.7 million of expense for a valuation allowance recorded against foreign tax credit carryforwards, $3.9 million of benefit from the impact of the corporate rate reduction on net deferred tax liability balances, and an expense of $0.8 million for the write-off of certain deferred tax assets that will no longer be realized.