Shareholders' Equity (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 26, 2018	Sep. 27, 2017	Sep. 26, 2018	Sep. 27, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 27, 2017, defined benefit plans				$ (982)
Balance as of December 27, 2017, derivatives				(1,334)
Balance as of December 27, 2017				(2,316)
Amortization of net loss	[1]			84
Net change in fair value of derivatives				6,225
Reclassification of derivatives to interest expense, net	[2]			(241)
Income tax (expense) benefit related to defined benefit plans		$ (7)	$ (9)	(20)	$ (27)
Income tax (expense) benefit related to derivatives		1,583	$ 133	1,673	$ (1,249)
Income tax (expense) benefit related to items of other comprehensive loss				1,693
Balance as of September 26, 2018, defined benefit plans		(918)		(918)
Balance as of September 26, 2018, derivatives		3,459		3,459
Balance as of September 26, 2018		$ 2,541		2,541
Estimated reclassification from accumulated other comprehensive income to interest expense related to the interest rate swaps over the next 12 months				$ 600

[1] Before-tax amount related to our defined benefit plans that was reclassified from accumulated other comprehensive loss and included as a component of pension expense within general and administrative expenses in our Condensed Consolidated Statements of Income during the three quarters ended September 26, 2018.

[2] Amounts reclassified from accumulated other comprehensive loss into income represent payments either received from or made to the counterparty for the effective portions of the interest rate swaps. These amounts are included as a component of interest expense, net in our Condensed Consolidated Statements of Income. We expect to make payments to the counterparty and reclassify approximately $0.6 million from accumulated other comprehensive loss related to our interest rate swaps during the next twelve months. See Note 9 for additional details.