Derivatives - Derivative Transactions Resulting in Hedged Gas Contracts Outstanding (Details) - Forecast MMBTU in Thousands, MBbls in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2020 MMBTU $ / bbl $ / MMBtu MBbls	Sep. 30, 2020 MMBTU $ / bbl $ / MMBtu MBbls	Jun. 30, 2020 MMBTU $ / bbl $ / MMBtu MBbls	Dec. 31, 2021 MMBTU $ / bbl $ / MMBtu MBbls
Fixed Price Oil Swaps (Brent)
Derivative [Line Items]
Hedged volume (MBbls) | MBbls	2,208	2,208	2,184	3,282
Weighted-average price ($/Bbl) | $ / bbl	59.85	59.85	59.91	47.19
Fixed Price Oil Swaps (WTI)
Derivative [Line Items]
Hedged volume (MBbls) | MBbls	0	0	30	0
Weighted-average price ($/Bbl) | $ / bbl	0.00	0.00	61.75	0.00
Purchased Oil Calls Options (Brent)
Derivative [Line Items]
Hedged volume (MBbls) | MBbls	276	276	273	0
Weighted-average price ($/Bbl) | $ / bbl	65.00	65.00	65.00	0.00
Fixed Price Gas Purchase Swaps (Kern, Delivered)
Derivative [Line Items]
Weighted-average price ($/MMBtu) | $ / MMBtu	2.73	2.89	2.89	2.62
Hedged volume (MMBtu) | MMBTU	3,840	5,060	5,005	8,500
Fixed Price Gas Purchase Swaps (SoCal Citygate)
Derivative [Line Items]
Weighted-average price ($/MMBtu) | $ / MMBtu	3.80	3.80	3.80	0.00
Hedged volume (MMBtu) | MMBTU	155	460	455	0