Derivative Financial Instruments (Details 4) $ in Millions	Mar. 31, 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	$ 9
Securities pledged as collateral to counterparties	20
Collateral posted under MNAs, credit-risk-contingent provisions in a liability position	$ (10)	$ (13)
Credit Derivatives
Number of counter- parties | counter-party	9	9
Notional amount	$ 475	$ 547
Credit exposure	13	17
Exposure, net of collateral	7	7
Gross liability fair value of contracts containing credit-risk-contingent features	24	21
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(8)	(3)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	(10)	(13)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 6	$ 5
AA-
Credit Derivatives
Number of counter- parties | counter-party	2	0
Notional amount	$ 90	$ 0
Credit exposure	3	0
Exposure, net of collateral	$ 3	$ 0
A plus
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 196	$ 82
Credit exposure	5	5
Exposure, net of collateral	$ 1	$ 0
A
Credit Derivatives
Number of counter- parties | counter-party	4	5
Notional amount	$ 140	$ 375
Credit exposure	2	9
Exposure, net of collateral	$ 0	$ 6
A-
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 16	$ 41
Credit exposure	3	3
Exposure, net of collateral	$ 3	$ 0
BBB+
Credit Derivatives
Number of counter- parties | counter-party	1	2
Notional amount	$ 33	$ 49
Credit exposure	0	0
Exposure, net of collateral	$ 0	$ 1