Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details 5) $ in Millions	Dec. 31, 2015 USD ($) counter-party	Dec. 31, 2014 USD ($) counter-party
Derivative Financial Instruments and Off-balance sheet Financial Instruments
Cash and securities pledged as collateral by counterparties	$ 14
Securities pledged as collateral to counterparties	13
Collateral posted under MNAs, credit-risk-contingent provisions in a liability position	$ (13)	$ (7)
Credit Derivatives
Number of counter-parties | counter-party	9	7
Notional amount	$ 547	$ 353
Credit exposure	17	5
Exposure, net of collateral	7	3
Gross liability fair value of contracts containing credit-risk-contingent features	21	16
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(3)	(4)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	(13)	(7)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 5	$ 5
A+
Credit Derivatives
Number of counter-parties | counter-party	1	1
Notional amount	$ 82	$ 164
Credit exposure	5	2
Exposure, net of collateral	$ 0	$ 1
A
Credit Derivatives
Number of counter-parties | counter-party	5	3
Notional amount	$ 375	$ 118
Credit exposure	9	3
Exposure, net of collateral	$ 6	$ 2
A-
Credit Derivatives
Number of counter-parties | counter-party	1	1
Notional amount	$ 41	$ 8
Credit exposure	3	0
Exposure, net of collateral	$ 0	$ 0
BBB+
Credit Derivatives
Number of counter-parties | counter-party	2	1
Notional amount	$ 49	$ 11
Credit exposure	0	0
Exposure, net of collateral	$ 1	$ 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