Oil and Gas Assets (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Oil and Gas Property, Full Cost Method, Gross	$ 15,786		$ 16,407
Oil and Gas Property, Full Cost Method, Depletion	7,915		8,306
Oil and Gas Property, Full Cost Method, Net	7,871		8,101
Oil and gas properties:
Subject to amortization	14,348		15,107
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	1,438		1,300
Accumulated depreciation and amortization	(81)		(69)
Net other property and equipment	180		174
Cost of oil and gas properties not subject to amortization
Acquisition costs	824
Exploration costs	354
Development costs	64
Fee mineral interests	24
Capitalized interest	172
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	1,438		1,300
Oil and Gas Assets (Textuals) [Abstract]
Non Strategic Assets Sold	588
Proceeds from Sale of Oil and Gas Property and Equipment	616	25
Furniture and Fixtures [Member]
Oil and gas properties:
Other property and equipment	150		139
Gas Gathering and Processing Equipment [Member]
Oil and gas properties:
Other property and equipment	111		104
Costs incurred in 2014 not subject to amortization [Member]
Oil and gas properties:
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	527
Cost of oil and gas properties not subject to amortization
Acquisition costs	129
Exploration costs	345
Development costs	14
Fee mineral interests	0
Capitalized interest	39
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	527
Costs incurred in 2013 not subject to amortization [Member]
Oil and gas properties:
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	262
Cost of oil and gas properties not subject to amortization
Acquisition costs	199
Exploration costs	1
Development costs	8
Fee mineral interests	1
Capitalized interest	53
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	262
Costs incurred in 2012 not subject to amortization [Member]
Oil and gas properties:
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	185
Cost of oil and gas properties not subject to amortization
Acquisition costs	86
Exploration costs	1
Development costs	31
Fee mineral interests	0
Capitalized interest	67
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	185
Costs incurred in 2011 and prior not subject to amortization [Member]
Oil and gas properties:
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	464
Cost of oil and gas properties not subject to amortization
Acquisition costs	410
Exploration costs	7
Development costs	11
Fee mineral interests	23
Capitalized interest	13
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative	$ 464