Risk Management - Energy Commodity Price Risk Management (Details) - Energy commodity derivative contracts	3 Months Ended
	Mar. 31, 2020 MMBbls Bcf
Short | Derivatives designated as hedging instruments | Crude oil fixed price
Derivative [Line Items]
Net open position long/(short)	18.9
Short | Derivatives designated as hedging instruments | Crude oil basis
Derivative [Line Items]
Net open position long/(short)	6.2
Short | Derivatives designated as hedging instruments | Natural gas fixed price
Derivative [Line Items]
Net open position long/(short) | Bcf	35.7
Short | Derivatives designated as hedging instruments | Natural gas basis
Derivative [Line Items]
Net open position long/(short) | Bcf	31.3
Short | Derivatives designated as hedging instruments | NGL fixed price
Derivative [Line Items]
Net open position long/(short)	1.2
Short | Derivatives not designated as hedging instruments | Crude oil fixed price
Derivative [Line Items]
Net open position long/(short)	0.7
Short | Derivatives not designated as hedging instruments | Crude oil basis
Derivative [Line Items]
Net open position long/(short)	2.4
Short | Derivatives not designated as hedging instruments | Natural gas fixed price
Derivative [Line Items]
Net open position long/(short) | Bcf	17.3
Short | Derivatives not designated as hedging instruments | NGL fixed price
Derivative [Line Items]
Net open position long/(short)	1.7
Long | Derivatives not designated as hedging instruments | Natural gas basis
Derivative [Line Items]
Net open position long/(short) | Bcf	23.4