Revenues Contract Balances (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 27, 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		521
Revenue recognized	[1]	(1,710)
Balance, June 27, 2018		21,430
Less current portion included in other current liabilities		3,292
Deferred franchise revenue included in other noncurrent liabilities		18,138
Revenue recognized that was included in either the deferred franchise revenue balance as of December 27, 2017 or the cumulative effect adjustment		1,700
Gift card liabilities		4,463		$ 6,480
Revenue recognized from gift card redemptions		$ 1,100

[1] Of this amount $1.7 million was included in either the deferred franchise revenue balance as of December 27, 2017 or the cumulative effect adjustment.