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Commitments and Contingencies - Crude Oil Releases (Details)
$ in Millions
Sep. 30, 2017
USD ($)
Jan. 31, 2016
bbl
Mar. 31, 2013
bbl
Modisette Release [Member]      
Loss Contingencies [Line Items]      
Crude oil released (in barrels)   30  
Paline Release [Member]      
Loss Contingencies [Line Items]      
Crude oil released (in barrels)   350  
Magnolia Release [Member]      
Loss Contingencies [Line Items]      
Crude oil released (in barrels)     5,900
Accrual for environmental loss contingencies | $ $ 1.0