Oil and Natural Gas Property Transactions - Narrative (Details) MMcf in Millions		3 Months Ended		9 Months Ended
	Oct. 29, 2018 USD ($) a well day $ / BTU	Sep. 30, 2018 USD ($) well	Sep. 30, 2017 USD ($) well MMcf	Sep. 30, 2018 USD ($) a well	Sep. 30, 2017 USD ($) a well MMcf
Business Acquisition [Line Items]
Proceeds from divestitures of proved and unproved properties				$ 395,000,000	$ 1,193,000,000
Mid-Continent [Member]
Business Acquisition [Line Items]
Productive gas wells, number of wells, net | well		3,200		3,200
Proceeds from divestitures of proved and unproved properties				$ 491,000,000
Number of net acres | a				238,500
Other properties [Member]
Business Acquisition [Line Items]
Proceeds from divestitures of proved and unproved properties		$ 8,000,000	$ 248,000,000	$ 31,000,000	$ 331,000,000
Haynesville Shale [Member]
Business Acquisition [Line Items]
Productive gas wells, number of wells, net | well			576		576
Proceeds from divestitures of proved and unproved properties					$ 915,000,000
Number of net acres | a					119,500
Haynesville Shale [Member] | Natural gas [Member]
Business Acquisition [Line Items]
Proved developed reserves (volume) | MMcf			80		80
Subsequent Event [Member] | Utica Shale [Member] | Disposal group, disposed of by sale, not discontinued operations [Member]
Business Acquisition [Line Items]
Area of land, gross (in acres) | a	1,500,000
Area of land, net (in acres) | a	900,000
Productive gas wells, number of wells, net | well	920
Consideration received	$ 1,900,000,000
Subsequent Event [Member] | Utica Shale [Member] | Disposal group, disposed of by sale, not discontinued operations [Member] | Commercial Shale [Member]
Business Acquisition [Line Items]
Area of land, net (in acres) | a	320,000
Subsequent Event [Member] | Future natural gas prices [Member] | Utica Shale [Member] | Disposal group, disposed of by sale, not discontinued operations [Member]
Business Acquisition [Line Items]
Consideration received	$ 100,000,000
Period of trading days | day	20
Consecutive trading days | day	30
Subsequent Event [Member] | 2022 NYMEX Natural Gas [Member] | Future natural gas prices [Member] | Utica Shale [Member] | Disposal group, disposed of by sale, not discontinued operations [Member]
Business Acquisition [Line Items]
Consideration received	$ 50,000,000
Subsequent Event [Member] | 2022 NYMEX Natural Gas [Member] | Future Natural Gas Prices Twenty Twenty Two [Member] | Utica Shale [Member] | Disposal group, disposed of by sale, not discontinued operations [Member]
Business Acquisition [Line Items]
Average Sales Prices | $ / BTU	3.00
Subsequent Event [Member] | 2022 NYMEX Natural Gas [Member] | Future Natural Gas Prices Twenty Twenty Three [Member] | Utica Shale [Member] | Disposal group, disposed of by sale, not discontinued operations [Member]
Business Acquisition [Line Items]
Average Sales Prices | $ / BTU	3.25