Derivatives Derivatives (Midland Crude Oil Basis Swap) (Details) - Fuel Product - Not Designated as Hedging Instrument - Midland crude oil basis swap purchases	Dec. 31, 2019 bbl	Dec. 31, 2018 bbl $ / bbl
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		1,275,000
Average Swap ($/Bbl) | $ / bbl		(12.27)
First Quarter 2019 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	0	501,500
Barrels per Day Purchased		5,572
Average Swap ($/Bbl) | $ / bbl		(12.79)
Second Quarter 2019 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		773,500
Barrels per Day Purchased		8,500
Average Swap ($/Bbl) | $ / bbl		(11.74)