Commitments and Contingencies Crude Oil Releases (Details) $ in Millions	Dec. 31, 2017 USD ($)	Jan. 31, 2016 bbl	Apr. 28, 2015 bbl	Mar. 31, 2013 bbl
Modisette Release
Loss Contingencies [Line Items]
Barrels of crude oil released		30
Paline Release
Loss Contingencies [Line Items]
Barrels of crude oil released		350
Fouke Junction Crude Oil Release
Loss Contingencies [Line Items]
Barrels of crude oil released			130
Magnolia Station Spill
Loss Contingencies [Line Items]
Barrels of crude oil released				5,900
Accrual for environmental loss contingencies | $	$ 1.0