Fair Value Measurements (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended						3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Cost and equity method investments [Member]	Sep. 30, 2011 Cost and equity method investments [Member]	Sep. 30, 2012 Cost and equity method investments [Member]	Sep. 30, 2011 Cost and equity method investments [Member]	Sep. 30, 2012 Long Lived Assets, Including Real Estate [Member]	Sep. 30, 2011 Long Lived Assets, Including Real Estate [Member]	Sep. 30, 2012 Long Lived Assets, Including Real Estate [Member]	Sep. 30, 2011 Long Lived Assets, Including Real Estate [Member]	Sep. 30, 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]	Sep. 30, 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]	Sep. 30, 2012 Private Equity And Real Estate Funds [Member]	Sep. 30, 2011 Private Equity And Real Estate Funds [Member]	Sep. 30, 2012 Private Equity And Real Estate Funds [Member]	Sep. 30, 2011 Private Equity And Real Estate Funds [Member]	Dec. 31, 2011 Private Equity And Real Estate Funds [Member]	Sep. 30, 2012 Real Estate Equity Properties And Investments [Member]	Sep. 30, 2011 Real Estate Equity Properties And Investments [Member]	Sep. 30, 2012 Real Estate Equity Properties And Investments [Member]	Sep. 30, 2011 Real Estate Equity Properties And Investments [Member]	Sep. 30, 2012 Retained Interest [Member]	Jun. 30, 2012 Retained Interest [Member]	Dec. 31, 2011 Retained Interest [Member]	Sep. 30, 2011 Retained Interest [Member]	Jun. 30, 2011 Retained Interest [Member]	Dec. 31, 2010 Retained Interest [Member]	Sep. 30, 2012 Retained Interest [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Retained Interest [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2012 Derivatives [Member]	Jun. 30, 2012 Derivatives [Member]	Dec. 31, 2011 Derivatives [Member]	Sep. 30, 2011 Derivatives [Member]	Jun. 30, 2011 Derivatives [Member]	Dec. 31, 2010 Derivatives [Member]	Sep. 30, 2012 Other 1 [Member]	Jun. 30, 2012 Other 1 [Member]	Dec. 31, 2011 Other 1 [Member]	Sep. 30, 2011 Other 1 [Member]	Jun. 30, 2011 Other 1 [Member]	Dec. 31, 2010 Other 1 [Member]
Cumulative gain (loss) adjustment for non performance risk	$ 21		$ 21		$ 13
Investments, Fair Value Disclosure																																	29	35
Cash Accruals Not Included In Schedule Assets Measured For Fair Value On Recurring Basis	4	6	4	6
Fair value assets measured on non recurring basis	1,862		1,862											336	403	1,565	3,282	82		82		123
Adjustments To Assets Measured At Fair Value On Non Recurring Basis						(50)	(84)	(105)	(257)	(451)	(368)	(651)	(1,265)					(1)	(3)	(3)	(16)
Impairment of Long-Lived Assets Held-for-use																							71	223	126	999
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3,123		3,123																								29	31	35	37	45	39			358	348	369	299	297	265	781	785	817	1,024	1,149	906
Individually Insignificant Recurring Fair Value Measurements	312		312
Individually Insignificant NonRecurring Fair Value Measurements	$ 367		$ 367