Oil and Natural Gas Property Transactions - Narrative (Details) MMcf in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) a well	Dec. 31, 2017 USD ($) a well MMcf	Mar. 31, 2017 USD ($)
Business Acquisition [Line Items]
Proceeds from divestitures of proved and unproved properties	$ 319		$ 892
Mid-Continent [Member]
Business Acquisition [Line Items]
Proceeds from divestitures of proved and unproved properties	$ 420
Number of net acres | a	171,000
Productive gas wells, number of wells, net | well	2,150
Haynesville Shale [Member]
Business Acquisition [Line Items]
Proceeds from divestitures of proved and unproved properties		$ 915
Number of net acres | a		119,500
Productive gas wells, number of wells, net | well		576
Haynesville Shale [Member] | Natural gas [Member]
Business Acquisition [Line Items]
Proved developed reserves (volume) | MMcf		80
Other properties [Member]
Business Acquisition [Line Items]
Proceeds from divestitures of proved and unproved properties	$ 18	$ 20