Derivative Financial Instruments (Summary of recognized gains (losses) related to derivative financial instruments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net		$ (1)	$ 51
Derivative instruments, gain (loss) recognized in income, net		(2)	49
Interest rate swaps [Member]
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net			61
Credit default swap - purchased protection [Member]
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net		(1)	(47)
Credit default swap - sold protection [Member]
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net			3
Total return swaps [Member]
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net			(2)
Futures sold, not yet purchased [Member]
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net			21
Gain (loss) on derivative instruments held for trading purposes, net		(1)	(2)
Options written [Member]
Recognized Gains (Losses)
Derivative instruments not designated as hedging instruments, gain (loss), net			$ 15