Debt and Financing Obligations - Financing Obligations (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Jun. 29, 2016 USD ($) location	Jun. 01, 2015 USD ($) item	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Financing Obligations
Financing obligations			$ 147,400		$ 147,400		$ 148,127
Net loss (gain) on sale and disposition of assets			(811)	$ (1,128)	(68)	$ (575)
Capitol Petroleum Group
Financing Obligations
Financing obligations			86,600		86,600
Financing obligations, ASC840		$ 89,600
Number of sale-leaseback transactions | item		2
Interest expense			2,300	2,300	4,600	4,700
Lease rental payments			2,500	2,400	5,000	4,900
Number of sites under financing obligation | item		53
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member] | Sale Leaseback Sites [Member]
Financing Obligations
Financing obligations			62,200		62,200
Financing obligations, ASC840	$ 62,500
Interest expense			1,100	1,100	2,200	2,200
Lease rental payments			$ 1,100	$ 1,100	$ 2,300	$ 2,200
Number of sites under financing obligation | location	30
Sale leaseback, gross proceeds ASC840	$ 63,500
Sale leaseback financing fees ASC840	$ 1,000