Derivative Financial Instruments (Details 4) $ in Millions	Jun. 30, 2016 USD ($) counter-party	Dec. 31, 2015 USD ($) counter-party
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash and securities pledged as collateral by counterparties	$ 6
Securities pledged as collateral to counterparties	30
Collateral posted under MNAs, credit-risk-contingent provisions in a liability position	(7)	$ (13)
Collateral already posted, aggregate fair value, without credit-risk-contingent features	$ 23
Credit Derivatives
Number of counter- parties | counter-party	8	9
Notional amount	$ 339	$ 547
Credit exposure	8	17
Exposure, net of collateral	3	7
Gross liability fair value of contracts containing credit-risk-contingent features	25	21
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(14)	(3)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	(7)	(13)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 4	$ 5
AA-
Credit Derivatives
Number of counter- parties | counter-party	2	0
Notional amount	$ 67	$ 0
Credit exposure	1	0
Exposure, net of collateral	$ 1	$ 0
A plus
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 207	$ 82
Credit exposure	5	5
Exposure, net of collateral	$ 2	$ 0
A
Credit Derivatives
Number of counter- parties | counter-party	3	5
Notional amount	$ 58	$ 375
Credit exposure	2	9
Exposure, net of collateral	$ 0	$ 6
A-
Credit Derivatives
Number of counter- parties | counter-party	0	1
Notional amount	$ 0	$ 41
Credit exposure	0	3
Exposure, net of collateral	$ 0	$ 0
BBB+
Credit Derivatives
Number of counter- parties | counter-party	2	2
Notional amount	$ 7	$ 49
Credit exposure	0	0
Exposure, net of collateral	$ 0	$ 1