Fair Value Measurements (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			3 Months Ended																			3 Months Ended			3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Cost and equity method investments [Member]	Mar. 31, 2012 Cost and equity method investments [Member]	Mar. 31, 2013 Long Lived Assets, Including Real Estate [Member]	Mar. 31, 2012 Long Lived Assets, Including Real Estate [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Cost and equity method investments [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Cost and equity method investments [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Long Lived Assets, Including Real Estate [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Long Lived Assets, Including Real Estate [Member]	Dec. 31, 2012 Retained Interest [Member]	Mar. 31, 2012 Retained Interest [Member]	Dec. 31, 2011 Retained Interest [Member]	Mar. 31, 2013 Retained Interest [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Retained Interest [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2013 Derivatives [Member]	Dec. 31, 2012 Derivatives [Member]	Mar. 31, 2012 Derivatives [Member]	Dec. 31, 2011 Derivatives [Member]	Mar. 31, 2012 Other 1 [Member]	Dec. 31, 2011 Other 1 [Member]	Mar. 31, 2013 Private Equity And Real Estate Funds [Member]	Mar. 31, 2012 Private Equity And Real Estate Funds [Member]	Dec. 31, 2012 Private Equity And Real Estate Funds [Member]	Mar. 31, 2013 Real Estate Equity Properties And Investments [Member]	Mar. 31, 2012 Real Estate Equity Properties And Investments [Member]
Fair Value Of Securities Transferred Between Level One And Level Two	$ 2
Cumulative gain (loss) adjustment for non performance risk	18		15														(18)	(15)
Investments, Fair Value Disclosure															91	83
Cash Accruals Not Included In Schedule Assets Measured For Fair Value On Recurring Basis	4	4
Fair value assets measured on non recurring basis	1,432	2,412						203	313	2,050	2,182												20		84
Adjustments To Assets Measured At Fair Value On Non Recurring Basis				(72)	(21)	(359)	(151)																(3)	(3)
Impairment of Long-Lived Assets Held-for-use																										223	50
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,907	2,990										83	34	35				262	117	141	390	388
Individually Insignificant Recurring Fair Value Measurements	233	233
Individually Insignificant NonRecurring Fair Value Measurements	$ 367	$ 285