Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Effective tax rate	0.00%	(15.00%)	(86.00%)
Alternative minimum tax carryforward, expected refund	$ 30,000,000
Sequestered amount relating to alternative minimum tax refunds		$ 2,000,000
Income tax refund received		32,000,000	$ 1,000,000
Valuation allowance, deferred tax asset, Amount			522,000,000
Effective income tax rate reconciliation, change in deferred tax assets valuation allowance, amount	(2,000,000)	$ (1,034,000,000)	$ 522,000,000
Operating loss carryforward valuation allowance	59,000,000
Unrecognized tax benefits that would impact effective tax rate	0
Indigo Natural Resources, LLC
Income Taxes [Line Items]
Operating loss carryforwards subject to a section 382 limitation	48,000,000
Montage Resources Corporation
Income Taxes [Line Items]
Operating loss carryforwards subject to a section 382 limitation	1,700,000
Net operating loss carryforward	858,000,000
Statutory depletion carryforward
Income Taxes [Line Items]
Tax credit carryforward	13,000,000
Interest deduction carryforward
Income Taxes [Line Items]
Tax credit carryforward	46,000,000
Exploration Program in Canada
Income Taxes [Line Items]
Net operating loss carryforward	29,000,000
Federal
Income Taxes [Line Items]
Operating loss carryforwards subject to a section 382 limitation	2,000,000,000
Operating loss carryforwards, subject to expiration	3,000,000,000
Operating loss carryforwards, not subject to expiration	1,000,000,000
Net operating loss carryforward	$ 4,000,000,000