Summary of Significant Accounting Policies - Leases (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($) lease	Mar. 31, 2019 USD ($)
Leases
Number of franchisees' leases recognized by the Company	0
Number of sublease agreements	4
Sublease Income \| $	$ 0.4	$ 0.4

Amount of sublease income excluding finance and operating lease expense.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971

Name:	us-gaap_SubleaseIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration