Impairment Of Long-Lived Assets And Other Lease Charges Closed Restaurant Reserve Activity (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Closed-restaurant reserve, beginning of the period	$ 1,352
Provisions for restaurant closures	41	$ 249
Changes in estimates of accrued costs	(11)	(147)
Payments, net	(144)	(889)
Other adjustments, including the effect of discounting future obligations	23	111
Closed-restaurant reserve, end of the period	$ 1,261	$ 2,028