Revenue from Contracts with Customers - Additional Information (Details)	3 Months Ended	9 Months Ended
	Mar. 28, 2018 USD ($)	Sep. 25, 2019 USD ($)	Sep. 26, 2018 USD ($) restaurant	Sep. 25, 2019 restaurant	Sep. 25, 2019	Sep. 25, 2019 USD ($)	Dec. 26, 2018 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Loyalty Rewards Program, Points Needed For One Reward		$ 100
Loyalty Rewards Program, Award Earned		$ 10
Loyalty Rewards Program, Expiration Period For Inactivity		6 years
Revenue allocated to loyalty points not redeemed						$ 900,000	$ 1,000,000
Loyalty rewards program, expected loyalty points redemption period (in years)		1 year
Additional contract liability		$ 1,367,000	$ 277,000
Franchise license
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Franchise agreement term (in years)		20 years
Franchise agreement renewal term (in years)		20 years
Hardware Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unsatisfied performance obligations						$ 0
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Satisfied over renewal term (in years)		10 years
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Satisfied over renewal term (in years)		20 years
Accounting Standards Update 2014-09 | Retained Earnings
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative catch-up adjustment	$ 3,500,000
CALIFORNIA
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of Restaurants				1	4
ARIZONA
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of Restaurants			1		7
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Additional contract liability			$ 700,000