Derivative and Hedging Activities - Fair Value Level 3 Measurements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	$ 130
Balance, end of period	(118)	$ 130
Energy related derivative
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	130
Balance, end of period	(118)	130
Fair value, inputs, level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	12
Balance, end of period	8	12
Fair value, inputs, level 3 | Commodity contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	12	87
Total gains (losses) (realized/unrealized): Included in earnings	11	(59)
Total purchases, issuances, sales and settlements: Settlements	(15)	(16)
Balance, end of period	8	12
Fair value, inputs, level 3 | Commodity contracts | Oil, natural gas and NGL sales
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total gains (losses) (realized/unrealized): Included in earnings	11	(59)
Change in unrealized gains (losses) related to assets still held at reporting date	0	(19)
Fair value, inputs, level 3 | Energy related derivative | Future natural gas prices | Utica Contingent Consideration
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	0	7
Total gains (losses) (realized/unrealized): Included in earnings	0	(7)
Total purchases, issuances, sales and settlements: Settlements	0	0
Balance, end of period	0	0
Fair value, inputs, level 3 | Energy related derivative | Future natural gas prices | Utica Contingent Consideration | Oil, natural gas and NGL sales
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total gains (losses) (realized/unrealized): Included in earnings	0	(7)
Change in unrealized gains (losses) related to assets still held at reporting date	$ 0	$ 0