Derivatives and Hedging Activities (Details 6) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Fair value of credit derivatives purchased and sold
Credit derivatives purchased	$ (3)	$ (7)	$ 10
Credit derivatives sold	3	11	(8)
Credit derivative, net	0	4	2
Credit derivatives sold and held
Credit derivative, notional amount	1,051	1,179	1,239
Credit derivative payment/performance risk percentage		9.04%
Single name credit default swaps [Member]
Fair value of credit derivatives purchased and sold
Credit derivatives purchased	(4)	(10)	3
Credit derivatives sold	1	9	(1)
Credit derivative, net	(3)	(1)	2
Credit derivatives sold and held
Credit derivative, notional amount	550	844	878
Credit derivative, average term (years)	2 years 5 months 1 day	2 years 4 months 24 days	2 years 2 months 5 days
Credit derivative payment/performance risk percentage	4.40%	4.45%	4.98%
Traded credit default swap indices [Member]
Fair value of credit derivatives purchased and sold
Credit derivatives purchased			6
Credit derivatives sold	3	2	(6)
Credit derivative, net	3	2
Credit derivatives sold and held
Credit derivative, notional amount	478	318	343
Credit derivative, average term (years)	2 years 9 months 4 days	3 years 10 months 17 days	3 years 2 months 12 days
Credit derivative payment/performance risk percentage	1.87%	3.47%	4.58%
Others [Member]
Fair value of credit derivatives purchased and sold
Credit derivatives purchased	1	3	1
Credit derivatives sold	(1)		(1)
Credit derivative, net		3
Credit derivatives sold and held
Credit derivative, notional amount	$ 23	$ 17	$ 18
Credit derivative, average term (years)	5 years 5 months 23 days	5 years 6 months 22 days	5 years 8 months 27 days
Credit derivative payment/performance risk percentage	9.74%		10.89%