Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2017	Dec. 28, 2016
Receivables:
Trade accounts receivable from franchisees	$ 10,688	$ 10,513
Financing receivables from franchisees	5,084	2,804
Allowance for doubtful accounts	(276)	(280)
Total current receivables, net	21,384	19,841
Noncurrent assets (included as a component of other noncurrent assets):
Notes receivable from franchisees	427	732
Write-off of financing receivables from a franchisee	200
Vendor receivables [Member]
Receivables:
Other receivable, gross, current	3,256	3,865
Credit card receivables [Member]
Receivables:
Other receivable, gross, current	1,870	1,678
Other [Member]
Receivables:
Other receivable, gross, current	762	$ 1,261
Insurance receivable, current	$ 400