Derivative Financial Instruments (Details 5) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013 party	Dec. 31, 2012 party
Derivative Financial Instruments
Cash and securities pledged as collateral by counterparties	$ 7
Securities pledged as collateral to counterparties	21
Collateral posted under MNAs for contracts without credit-risk-contingent liabilities	12
Credit Derivatives
Number of counter-parties	8	7
Notional amount	1,913	6,199
Credit exposure	10	24
Exposure, net of collateral	5	1
Gross liability fair value of contracts containing credit-risk-contingent features	19	62
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(10)	(28)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	(9)	(25)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently		9
A+
Credit Derivatives
Number of counter-parties	1	1
Notional amount	887	19
Credit exposure	2
Exposure, net of collateral	2
A
Credit Derivatives
Number of counter-parties	4	3
Notional amount	123	2,252
Credit exposure	3	12
Exposure, net of collateral	1
A-
Credit Derivatives
Number of counter-parties	2	2
Notional amount	94	311
Credit exposure	1	1
Exposure, net of collateral	1	1
BBB+
Credit Derivatives
Number of counter-parties	1	1
Notional amount	809	3,617
Credit exposure	4	11
Exposure, net of collateral	$ 1