Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Blue Racer	Mar. 31, 2013 Blue Racer Line TL-404	Sep. 30, 2013 Blue Racer Line TL-404	Sep. 30, 2013 Categories of Investments, Marketable Securities, Trading Securities	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities	Sep. 30, 2013 Cost method investments	Dec. 31, 2012 Cost method investments
Gain (Loss) on Investments [Line Items]
Assets Held-in-trust						$ 100	$ 95	$ 10	$ 14
Cash proceeds from sale of assets	595	0		47	83
Gain on sale of assets				25	75
After tax gain on sale of assets				14	42
Contribution of assets in exchange for additional ownership interest in Blue Racer	$ 473	$ 0	$ 473