Revenues Contract Balances (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 28, 2018	Dec. 28, 2017	Dec. 27, 2017
Revenues [Abstract]
Balance, December 27, 2017		$ 1,643
Cumulative effect adjustment recognized upon adoption of Topic 606			$ 20,976	$ 15,446
Fees received from franchisees		239
Revenue recognized	[1]	(930)
Balance, March 28, 2018		21,928
Less current portion included in other current liabilities		3,303
Deferred franchise revenue included in other noncurrent liabilities		18,625
Revenue recognized that was included in either the deferred franchise revenue balance as of December 27, 2017 or the cumulative effect adjustment		900
Gift card liabilities		4,419		$ 6,480
Revenue recognized from gift card redemptions		$ 700

[1] Of this amount $0.9 million was included in either the deferred franchise revenue balance as of December 27, 2017 or the cumulative effect adjustment.