Acquisition Narrative (Details) $ / shares in Units, $ in Thousands, shares in Millions								3 Months Ended								12 Months Ended
	Aug. 20, 2019 USD ($) restaurant	Jun. 11, 2019 USD ($) restaurant	Apr. 30, 2019 USD ($) restaurant $ / shares shares	Feb. 13, 2018 USD ($) restaurant	Nov. 28, 2017 USD ($)	Jun. 05, 2017 USD ($)	Feb. 28, 2017 USD ($)	Dec. 29, 2019 USD ($)	Sep. 29, 2019 USD ($)	Jun. 30, 2019 USD ($) restaurant	Mar. 31, 2019 USD ($)	Dec. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jul. 01, 2018 USD ($)	Apr. 01, 2018 USD ($)	Dec. 29, 2019 USD ($) restaurant	Dec. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2017 USD ($)
Business Acquisition [Line Items]
Revenue																$ 1,462,765	$ 1,179,307	$ 1,088,532
Restaurants Acquired										233		10			1	44
Acquisition of restaurants, net of cash acquired																$ (130,646)	(38,102)	(37,923)
Business Combination, Bargain Purchase, Gain Recognized, Amount				$ 230												0	230	0
Deferred income taxes								$ 47,200				$ 500				47,200	500		$ 6,700
Acquisition-related costs								2,800	$ 2,800	$ 2,600	$ 2,600	$ 400	$ 800	$ 100	$ 100
Business Combination, Retirement of Debt, Net of Cash Acquired			$ 113,800
Business Combination, Share Restriction			2 years
Business Combination Purchase Price Allocation, Common Stock			$ 145,300
Business Combination Purchase Price Allocation, Common Stock, Per Share | $ / shares			$ 9.81
2019 Acquisitions [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma, General and Administrative Exepnses																$ 4,100	$ 1,400
Restaurants Acquired | restaurant																234
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities								29								$ 29
Cambridge Holdings, LLC [Member]
Business Acquisition [Line Items]
Business Combination, Restaurants Acquired | restaurant			132
Business Combination, Construction Of Restaurants Acquired | restaurant			33
Business Combination, Restaurants Acquired Period			3 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities								44,292								$ 44,292
2018 Acquisitions [Member]
Business Acquisition [Line Items]
Restaurants Acquired | restaurant																44
Acquisition of restaurants, net of cash acquired																$ (38,102)
Acquisition-related costs																1,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities								346								346
2017 Acquisitions [Member]
Business Acquisition [Line Items]
Restaurants Acquired					4	17	43										64
Acquisition of restaurants, net of cash acquired					$ (1,202)	$ (16,355)	$ (20,366)										$ (37,923)
Acquisition-related costs																1,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities								$ 4,357								$ 4,357
Off-Market Favorable Lease [Member] | 2018 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																17 years 2 months
Off-Market Favorable Lease [Member] | 2017 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																	15 years 2 months
Above Market Leases [Member] | 2018 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																18 years 3 months
Above Market Leases [Member] | 2017 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																	14 years 3 months
Franchise Rights [Member]
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount				$ 290
Franchise Rights [Member] | 2019 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																32 years 8 months 12 days
Franchise Rights [Member] | 2018 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																31 years 7 months
Franchise Rights [Member] | 2017 Acquisitions [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life																	27 years 11 months
Common Stock [Member] | Cambridge Holdings, LLC [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares			7.4
Convertible Preferred Stock, Shares Issued upon Conversion | shares			7.5
Series C Preferred Stock [Member] | Cambridge Holdings, LLC [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares			0.0
NEW YORK | 2019 Acquisitions [Member]
Business Acquisition [Line Items]
Restaurants Acquired | restaurant	1	13	220													234
Acquisition of restaurants, net of cash acquired	$ (1,108)	$ (15,788)	$ (259,083)													$ (275,979)
NEW YORK | 2018 Acquisitions [Member]
Business Acquisition [Line Items]
Restaurants Acquired | restaurant				1
Acquisition of restaurants, net of cash acquired				$ 0
Restaurant sales
Business Acquisition [Line Items]
Revenue																1,452,516	$ 1,179,307	1,088,532
Restaurant sales | 2019 Acquisitions [Member]
Business Acquisition [Line Items]
Revenue																201,900
Restaurant sales | 2018 Acquisitions [Member]
Business Acquisition [Line Items]
Revenue																52,900	16,900
Restaurant sales | 2017 Acquisitions [Member]
Business Acquisition [Line Items]
Revenue																	90,200	64,900
Other revenue
Business Acquisition [Line Items]
Revenue																$ 10,249	$ 0	$ 0