Fair Value Measurements (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended										12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Cost and equity method investments [Member]	Dec. 31, 2011 Cost and equity method investments [Member]	Dec. 31, 2012 Long Lived Assets, Including Real Estate [Member]	Dec. 31, 2011 Long Lived Assets, Including Real Estate [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Cost and equity method investments [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 3 [Member] Cost and equity method investments [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Long Lived Assets, Including Real Estate [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 3 [Member] Long Lived Assets, Including Real Estate [Member]	Dec. 31, 2012 Private Equity And Real Estate Funds [Member]	Dec. 31, 2011 Private Equity And Real Estate Funds [Member]	Dec. 31, 2012 Real Estate Equity Properties And Investments [Member]	Dec. 31, 2011 Real Estate Equity Properties And Investments [Member]	Dec. 31, 2012 Retained Interest [Member]	Dec. 31, 2011 Retained Interest [Member]	Dec. 31, 2010 Retained Interest [Member]	Dec. 31, 2012 Retained Interest [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Retained Interest [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Derivatives [Member]	Dec. 31, 2011 Derivatives [Member]	Dec. 31, 2010 Derivatives [Member]	Dec. 31, 2012 Other Items [Member]	Dec. 31, 2011 Other Items [Member]	Dec. 31, 2010 Other Items [Member]
Cumulative gain (loss) adjustment for non performance risk																				$ 15	$ 11
Investments, Fair Value Disclosure																		83	35
Cash Accruals Not Included In Schedule Assets Measured For Fair Value On Recurring Basis	2	1
Fair value assets measured on non recurring basis	2,412						313	402	2,184	3,254	84	123
Adjustments To Assets Measured At Fair Value On Non Recurring Basis			(153)	(272)	(624)	(1,410)					(33)	(24)
Impairment of Long-Lived Assets Held-for-use													218	976
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,990														83	35	39			262	141	227	432	388	450
Individually Insignificant Recurring Fair Value Measurements	233
Individually Insignificant NonRecurring Fair Value Measurements	$ 287