Asset Impairments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	$ 97	$ 0
North Sea [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	92	0
Non-Core US Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	$ 5	$ 0