Significant Accounting Policies - Insurance Reserves and Derivatives (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Derivative Financial Instruments
Other comprehensive income (loss), before tax	$ 1,421,000	$ 1,492,000	$ (1,846,000)
Other comprehensive income (loss), net of tax	900,000	$ 900,000	$ (1,200,000)
Minimum
Insurance Reserves
Employee insurance retention limit per occurrence	100,000
Maximum
Insurance Reserves
Employee insurance retention limit per occurrence	$ 1,000,000