Revenues Financial Statement Impact of Adoption (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2018	Jun. 28, 2017	Jun. 27, 2018	Jun. 28, 2017	Dec. 28, 2017	Dec. 27, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid and other current assets	$ 12,040		$ 12,040			$ 11,788
Deferred income taxes	19,333		19,333			16,945
Other current liabilities	53,218		53,218			59,246
Other noncurrent liabilities	47,831		47,831			27,951
Deficit	(328,722)		(328,722)			(334,661)
Franchise and license revenue	54,593	$ 35,021	108,673	$ 69,152
Costs of franchise and license revenue	29,049	10,244	57,605	19,990
Provision for income taxes	2,578	4,930	4,407	9,674
Net income	$ 11,626	$ 8,749	$ 21,385	$ 17,122
Basic net income per share	$ 0.18	$ 0.13	$ 0.33	$ 0.24
Diluted net income per share	$ 0.18	$ 0.12	$ 0.32	$ 0.24
Total comprehensive income	$ 15,016	$ 7,219	$ 21,684	$ 14,983
Deferred income tax expense			2,896	6,291
Other current assets			(253)	3,587
Other accrued liabilities			(6,352)	(365)
Other noncurrent liabilities			(1,345)	(1,068)
Net cash flows provided by operating activities			26,096	$ 32,818
Cumulative effect adjustment recognized upon adoption of Topic 606					$ 20,976	$ (15,446)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid and other current assets	509		509
Deferred income taxes	(5,141)		(5,141)
Other current liabilities	(1,230)		(1,230)
Other noncurrent liabilities	(18,138)		(18,138)
Deficit	14,736		14,736
Franchise and license revenue	(20,949)		(41,256)
Costs of franchise and license revenue	(20,535)		(40,299)
Provision for income taxes	(107)		(247)
Net income	$ (307)		$ (710)
Basic net income per share	$ 0.00		$ (0.01)
Diluted net income per share	$ (0.01)		$ (0.01)
Total comprehensive income	$ (307)		$ (710)
Deferred income tax expense			(247)
Other current assets			(509)
Other accrued liabilities			851
Other noncurrent liabilities			615
Net cash flows provided by operating activities			0
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid and other current assets	12,549		12,549
Deferred income taxes	14,192		14,192
Other current liabilities	51,988		51,988
Other noncurrent liabilities	29,693		29,693
Deficit	(313,986)		(313,986)
Franchise and license revenue	33,644		67,417
Costs of franchise and license revenue	8,514		17,306
Provision for income taxes	2,471		4,160
Net income	$ 11,319		$ 20,675
Basic net income per share	$ 0.18		$ 0.32
Diluted net income per share	$ 0.17		$ 0.31
Total comprehensive income	$ 14,709		$ 20,974
Deferred income tax expense			2,649
Other current assets			(762)
Other accrued liabilities			(5,501)
Other noncurrent liabilities			(730)
Net cash flows provided by operating activities			26,096
Initial and other fees [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment recognized upon adoption of Topic 606					21,000
(Deficit) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment recognized upon adoption of Topic 606					100
Deferred Tax Asset [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment recognized upon adoption of Topic 606					(5,400)
Other Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment recognized upon adoption of Topic 606					(600)
Other Current Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment recognized upon adoption of Topic 606					500
Adjustments for New Accounting Pronouncement [Member] | (Deficit) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment recognized upon adoption of Topic 606					$ (15,600)
Initial and other fees [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Franchise and license revenue	400		1,000
Advertising [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Franchise and license revenue	19,500		38,800
Costs of franchise and license revenue	19,500		38,800
Other Franchise Services [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Franchise and license revenue	1,000		1,500
Costs of franchise and license revenue	$ 1,000		$ 1,500