Fair Value Measurements (Details 2) (Level 3 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended					3 Months Ended													3 Months Ended
	Mar. 31, 2012 Interest rate [Member]	Mar. 31, 2011 Interest rate [Member]	Mar. 31, 2011 Energy and commodity [Member]	Mar. 31, 2012 Energy and commodity [Member]	Dec. 31, 2011 Energy and commodity [Member]	Mar. 31, 2012 Credit [Member]	Mar. 31, 2011 Credit [Member]	Mar. 31, 2012 Principal Direct Investments [Member]	Mar. 31, 2011 Principal Direct Investments [Member]	Mar. 31, 2012 Principal Indirect Investments [Member]	Mar. 31, 2011 Principal Indirect Investments [Member]	Mar. 31, 2012 Equity and Mezzanine Direct Investments [Member]	Mar. 31, 2011 Equity and Mezzanine Direct Investments [Member]	Mar. 31, 2012 Equity and Mezzanine Indirect Investments [Member]	Mar. 31, 2011 Equity and Mezzanine Indirect Investments [Member]	Mar. 31, 2012 Mortgage Backed Securities, Other [Member]	Mar. 31, 2011 Mortgage Backed Securities, Other [Member]	Dec. 31, 2010 Mortgage Backed Securities, Other [Member]	Mar. 31, 2012 Other Debt Securities [Member]	Mar. 31, 2011 Other Debt Securities [Member]
Changes in Level 3 Fair Value Measurements
Beginning Balance	$ 38	$ 75	$ 1	$ (1)	$ (1)	$ (21)	$ 11	$ 225	$ 372	$ 473	$ 526	$ 15	$ 20	$ 36	$ 30	$ 35	$ 1	$ 1		$ 21
Gain (losses) included in earnings	(5)	4	(1)			(5)	(1)	1	2	23	33		5	1	(1)	2			3
Net transfers into (out of) Level 3		(3)
Purchases	1						(6)	1	28	10	14			3	2
Sales	(1)	2						(1)	7	(21)	25					32
Settlements						31								1	(1)				(3)	(21)
Transfers into Level 3	4	7
Transfers out of Level 3	(1)													(3)	3	4
Ending Balance	36	81		(1)	(1)	5	4	226	395	485	548	15	25	42	27	1	1	1
Unrealized gains (losses) included in earnings								$ 1	$ 2	$ 19	$ 24	$ 6	$ 10	$ 4	$ (4)				$ 3