Acquisitions and Divestitures (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended					3 Months Ended				3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2013 Wolfcamp [Member] Rate	Sep. 30, 2014 Sendero [Member]	Sep. 30, 2014 Gaines Dawson [Member]	Mar. 31, 2013 West Panhandle [Member]	Sep. 30, 2014 Barnett Shale Field [Member]	Mar. 31, 2014 Lease Contract through Year 2 [Member]	Mar. 31, 2014 Lease Contract for Year 3 [Member]	Sep. 30, 2014 Discontinued Operations [Member]	Sep. 30, 2013 Discontinued Operations [Member]	Sep. 30, 2014 Discontinued Operations [Member]	Sep. 30, 2013 Discontinued Operations [Member]	Sep. 30, 2014 Discontinued Operations [Member] Hugoton field [Member]	Sep. 30, 2014 Discontinued Operations [Member] Hugoton field [Member]	Sep. 30, 2014 Discontinued Operations [Member] Pioneer Alaska [Member]
Acquisitions and Divestitures [Line Items]
Gain on disposition of assets, net	$ (1,000,000)	$ 1,000,000	$ (11,000,000)	$ (206,000,000)	$ (181,000,000)	$ (1,000,000)	$ (2,000,000)	$ (22,000,000)				$ 0	$ 0	$ (5,000,000)	$ (9,000,000)
Proceeds from Divestiture of Interest in Consolidated Subsidiaries						31,000,000
Drilling rigs leased										12	8
Proceeds from Sale of Productive Assets			855,000,000	685,000,000	624,000,000		72,000,000	38,000,000	150,000,000							328,000,000		267,000,000
Goodwill, Written off Related to Sale of Business Unit																	2,000,000
Impairment of oil and gas properties												80,000,000	0	305,000,000	0
Maximum Payments From Related Party For Exploration Drilling And Completion Costs					$ 1,200,000,000
Payments From Related Party For Exploration Drilling And Completion Costs Percent					75.00%
Joint Venture Investment Ownership Percentage					40.00%