Debt and Financing Obligations - Financing Obligations (Details) $ in Thousands			3 Months Ended								12 Months Ended
	Jun. 29, 2016 USD ($) location	Jun. 01, 2015 USD ($) item	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Obligations
Financing obligations, ASC842			$ 148,127								$ 148,127
Financing obligations, ASC840							$ 149,997					$ 149,997
Number of locations acquired | item		53
Net loss (gain) on sale and disposition of assets			(2,400)	$ 300	$ (1,100)	$ 500	$ 100	$ 900	$ 3,000	$ 1,900	(2,730)	5,880	$ (1,624)
Sale Leaseback Sites [Member]
Financing Obligations
Financing obligations, ASC842			62,300								62,300
Financing obligations, ASC840	$ 62,500
Interest expense, ASC842											4,400
Interest expense for sale-leaseback properties, ASC840												4,400	4,400
Lease rental payments, ASC842											4,600
Lease rental payments, ASC840												4,500	4,500
Number of sites under financing obligation | location	30
Sale leaseback, gross proceeds ASC840	$ 63,500
Net loss (gain) on sale and disposition of assets											$ 0
Initial lease term											15 years
Number of 5-year options | item											2
Number of 10-year options | item											1
Sale leaseback financing fees ASC840	$ 1,000
Capitol Petroleum Group
Financing Obligations
Financing obligations, ASC842			$ 87,000								$ 87,000
Financing obligations, ASC840		$ 89,600
Number of sale-leaseback transactions | item		2
Interest expense, ASC842											9,300
Interest expense for sale-leaseback properties, ASC840												9,400	9,600
Lease rental payments, ASC842											$ 9,900
Lease rental payments, ASC840												$ 9,700	$ 9,700