Property (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2017	Dec. 28, 2016	Dec. 30, 2015
Property Owned [Abstract]
Total property owned	$ 344,164	$ 353,041
Less accumulated depreciation	227,959	241,132
Property owned, net	116,205	111,909
Property Held Under Capital Leases [Abstract]
Buildings, vehicles and other equipment held under capital leases	39,017	35,246
Less accumulated amortization	15,366	14,053
Property held under capital leases, net	23,651	21,193
Total property, net	139,856	133,102
Depreciation expense, including amortization of property under capital leases	21,200	20,600	$ 20,000
Franchised Units [Member]
Property Owned [Abstract]
Total property owned	70,438	76,088
Less accumulated depreciation	48,225	52,020
Property owned, net	22,213	24,068
Property Held Under Capital Leases [Abstract]
Buildings, vehicles and other equipment held under capital leases	6,060	5,656
Less accumulated amortization	3,300	3,408
Property held under capital leases, net	2,760	2,248
Total property, net	24,973	26,316
Land [Member]
Property Owned [Abstract]
Total property owned	32,506	29,914
Land [Member] | Franchised Units [Member]
Property Owned [Abstract]
Total property owned	15,490	16,192
Building and leasehold improvements [Member]
Property Owned [Abstract]
Total property owned	243,872	243,323
Building and leasehold improvements [Member] | Franchised Units [Member]
Property Owned [Abstract]
Total property owned	54,948	59,896
Other property and equipment [Member]
Property Owned [Abstract]
Total property owned	$ 67,786	$ 79,804