Derivative and Hedging Activities - Derivative Instruments (Details) - Energy related derivative $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021 USD ($) Bcf MMBbls	Dec. 31, 2020 USD ($) Bcf MMBbls
Derivative [Line Items]
Derivative assets (liabilities), at fair value, net	$ (375)	$ (118)
Oil
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | MMBbls	33,000,000	34,000,000
Derivative assets (liabilities), at fair value, net	$ (335)	$ (137)
Oil | Fixed-price swaps
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | MMBbls	27,000,000	27,000,000
Derivative assets (liabilities), at fair value, net	$ (333)	$ (136)
Oil | Basis protection swaps
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | MMBbls	6,000,000	7,000,000
Derivative assets (liabilities), at fair value, net	$ (2)	$ (1)
Natural Gas
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | Bcf	882,000,000	847,000,000
Derivative assets (liabilities), at fair value, net	$ (40)	$ 19
Natural Gas | Fixed-price swaps
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | Bcf	671,000,000	728,000,000
Derivative assets (liabilities), at fair value, net	$ (41)	$ 10
Natural Gas | Collars
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | Bcf	48,000,000	53,000,000
Derivative assets (liabilities), at fair value, net	$ 3	$ 8
Natural Gas | Basis protection swaps
Derivative [Line Items]
Derivative, nonmonetary notional amount, volume | Bcf	163,000,000	66,000,000
Derivative assets (liabilities), at fair value, net	$ (2)	$ 1