Derivative Financial Instruments (Details 4) $ in Millions	Sep. 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	$ 5
Securities pledged as collateral to counterparties	$ 32
Credit Derivatives
Number of counter- parties | counter-party	7	9
Notional amount	$ 376	$ 547
Credit exposure	5	17
Exposure, net of collateral	1	7
Gross liability fair value of contracts containing credit-risk-contingent features	6	21
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(1)	(3)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	0	(13)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 5	$ 5
A plus
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 63	$ 82
Credit exposure	3	5
Exposure, net of collateral	$ 0	$ 0
A
Credit Derivatives
Number of counter- parties | counter-party	4	5
Notional amount	$ 301	$ 375
Credit exposure	2	9
Exposure, net of collateral	$ 1	$ 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	$ 12	$ 49
Credit exposure	0	0
Exposure, net of collateral	$ 0	$ 1