Insurance Reserves - Changes in Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016
Insurance Reserves
Balance at the beginning of the period	$ 35,443	$ 30,550
Additions	47,032	42,508
Payments	(40,633)	(37,615)
Balance at the end of the period	$ 41,842	$ 35,443