Leases (Net Rental Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2017	Dec. 28, 2016	Dec. 30, 2015
Rental Expense:
Total rental expense	$ 33,021	$ 34,913	$ 36,780
Rental income:
Base rents	25,781	28,183	30,166
Contingent rents	5,042	5,337	5,305
Total rental income	30,823	33,520	35,471
Company-owned restaurants [Member]
Rental Expense:
Base rents	9,315	8,602	8,998
Contingent rents	3,168	3,351	3,134
Franchised and licensed restaurants [Member]
Rental Expense:
Base rents	17,674	19,883	21,751
Contingent rents	$ 2,864	$ 3,077	$ 2,897