Related Party Transactions - Joint Venture, Contributions From Parent, and Tax Narrative (Details)	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) tranche
Related party transactions
Cash contributions from parent	$ 0	$ 9,000,000
State income tax payable due to parent	0	$ 0
Investor
Related party transactions
Percent of estimated drilling, completion, and equipping costs of wells contributed by investor		60.00%
Number of investment tranches \| tranche		2
Working interest in joint venture wells		50.00%
Internal rate of return on invested capital in each tranche		12.00%
Working interest		15.00%
Capital costs reimbursed to company	91,000,000	$ 138,000,000
Related party accounts receivable	3,000,000	47,000,000
Related party accounts payable	7,000,000	20,000,000
Investor \| Investment Tranche One
Related party transactions
Funding from related party		$ 225,000,000
Investor \| Investment Tranche Two
Related party transactions
Funding from related party	$ 225,000,000

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