Operating Leases - Additional Information (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($) Store	Jun. 30, 2019 USD ($) Store	Dec. 31, 2018 USD ($)
Operating Leases [Line Items]
Non-cancelable operating leases obligation expiration period		2033
Weighted average remaining lease term	5 years 10 months 24 days	5 years 10 months 24 days
Number of retail sites leased to third party | Store	400	400
Variable lease payments	$ 0.5	$ 0.9
Short-term lease payments	0.1	0.3
Operating lease payments	$ 6.4	$ 12.8
Weighted average discount rate	6.90%	6.90%
Sublease rental income	$ 9.2	$ 18.7
Lessor operating lease term of expiration		through 2033
Deferred rent income under lease agreement	$ 6.9	$ 6.9	$ 6.3
Minimum [Member]
Operating Leases [Line Items]
Sublease contract term		1 year
Maximum [Member]
Operating Leases [Line Items]
Sublease contract term		10 years