Derivative Financial Instruments (Details 4) $ in Millions	Jun. 30, 2015 USD ($) counter-party	Dec. 31, 2014 USD ($) counter-party
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash and securities pledged as collateral by counterparties	$ 11
Securities pledged as collateral to counterparties	8
Collateral posted under MNAs, credit-risk-contingent provisions in a liability position	(7)	$ (7)
Collateral posted under MNAs for contracts without credit-risk-contingent liabilities	$ 1
Credit Derivatives
Number of counter- parties | counter-party	8	7
Notional amount	$ 1,065	$ 353
Credit exposure	13	5
Exposure, net of collateral	3	3
Gross liability fair value of contracts containing credit-risk-contingent features	14	16
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(5)	(4)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	(7)	(7)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 2	$ 5
A plus
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 98	$ 164
Credit exposure	3	2
Exposure, net of collateral	$ 1	$ 1
A
Credit Derivatives
Number of counter- parties | counter-party	4	3
Notional amount	$ 887	$ 118
Credit exposure	8	3
Exposure, net of collateral	$ 2	$ 2
A-
Credit Derivatives
Number of counter- parties | counter-party	2	1
Notional amount	$ 69	$ 8
Credit exposure	2	0
Exposure, net of collateral	$ 0	$ 0
BBB+
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 11	$ 11
Credit exposure	0	0
Exposure, net of collateral	$ 0	$ 0
BBB
Credit Derivatives
Number of counter- parties | counter-party	0	1
Notional amount	$ 0	$ 52
Credit exposure	0	0
Exposure, net of collateral	$ 0	$ 0