Organization and Summary of Significant Accounting Policies (Narrative) (Details)	1 Months Ended			3 Months Ended			9 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($) shares	Jan. 31, 2018 USD ($) shares	Jan. 31, 2015 shares	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Sep. 30, 2017 shares	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) derivative_position segment subsidiary $ / bbl $ / MMBTU shares	Dec. 31, 2018 USD ($) subsidiary derivative_position $ / bbl $ / MMBTU shares	Dec. 31, 2017 USD ($) derivative_position subsidiary $ / bbl $ / MMBTU	Jan. 01, 2019 USD ($)	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of segments | segment													2
Outstanding checks included in accounts payable	$ 34,000,000				$ 34,000,000								$ 15,000,000	$ 34,000,000
Natural gas, oil and NGL reserves discount													10.00%
Net unevaluated costs excluded from amortization, cumulative	1,755,000,000				1,755,000,000								$ 1,506,000,000	$ 1,755,000,000
Period of time needed to calculate ceiling value of reserves													12 months	12 months	12 months
Number of derivative positions designated for hedge accounting | derivative_position													0	0	0
Impairments													$ 16,000,000	$ 171,000,000	$ 0
Preferred stock dividend		$ 27,000,000											0	27,000,000	16,000,000
Preferred stock, common shares issued as stock dividend (in shares) | shares							10,040,306
Stock repurchase, authorized amount						$ 200,000,000
Treasury stock acquired	$ 201,000,000			$ 21,000,000	$ 180,000,000								$ 21,000,000	$ 180,000,000
Treasury stock (in shares) | shares	44,000,000			5,260,687	39,061,268								5,260,687	39,061,268
Treasury stock acquired, average cost per share (in dollars per share) | $ / shares				$ 3.84	$ 4.63
Shares held in trust (in shares) | shares	10,653				10,653								5,115	10,653
Shares held in trust, shares released (in shares) | shares														20,616
Operating lease assets													$ 159,000,000
Operating lease liability													153,000,000
Marketing-Related Intangible Assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Amortization of intangible asset								$ 5,000,000	$ 5,000,000	$ 5,000,000	$ 8,000,000	$ 9,000,000	9,000,000	$ 9,000,000	$ 9,000,000
Intangible Assets, Current	$ 65,000,000				$ 65,000,000								$ 56,000,000	$ 65,000,000
Accounting Standards Update 2016-02
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Operating lease assets																$ 105,000,000
Operating lease liability																$ 105,000,000
Natural Gas
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Average sales price ($ per unit) | $ / MMBTU													2.58	3.10	2.98
Oil
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Average sales price ($ per unit) | $ / bbl													55.69	65.56	47.79
NGL
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Average sales price ($ per unit) | $ / bbl													11.58	17.64	14.41
Royal Dutch Shell Plc
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of subsidiaries of major customer with which business is conducted | subsidiary													0	2	2
Common Stock
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued upon conversion (in shares) | shares		74,998,614
Depositary Shares
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued (in shares) | shares			34,500,000
WPX Property Acquisition
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Percentage of interest acquired																	86.00%
Discontinued operations, held-for-sale
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments						161,000,000								$ 160,000,000
Discontinued operations, held-for-sale | Marketing
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments						145,000,000								145,000,000
Discontinued operations, held-for-sale | Exploration and Production
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments						15,000,000								15,000,000
Other non-core assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments						$ 1,000,000							$ 16,000,000	$ 11,000,000
Customer concentration risk | Natural Gas, Oil and NGL | Sales Revenue
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Concentration percentage														10.40%	10.30%