Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details 5) $ in Millions	Dec. 31, 2016 USD ($) counter-party	Dec. 31, 2015 USD ($) counter-party
Credit Derivatives
Cash and securities pledged as collateral by counterparties	$ 5
Securities pledged as collateral to counterparties	4
Collateral posted under MNAs, credit-risk-contingent provisions in a liability position	$ 0	$ 7
Number of counter-parties | counter-party	5	9
Notional amount	$ 312	$ 312
Credit exposure	12	14
Exposure, net of collateral	9	6
Gross liability fair value of contracts containing credit-risk-contingent features	2	9
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(2)	(1)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	0	(7)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 0	$ 1
A plus
Credit Derivatives
Number of counter-parties | counter-party	5	1
Notional amount	$ 312	$ 82
Credit exposure	12	5
Exposure, net of collateral	$ 9	$ 0
A
Credit Derivatives
Number of counter-parties | counter-party	0	5
Notional amount	$ 0	$ 178
Credit exposure	0	6
Exposure, net of collateral	$ 0	$ 6
A-
Credit Derivatives
Number of counter-parties | counter-party	0	1
Notional amount	$ 0	$ 16
Credit exposure	0	3
Exposure, net of collateral	$ 0	$ 0
BBB plus
Credit Derivatives
Number of counter-parties | counter-party	0	2
Notional amount	$ 0	$ 36
Credit exposure	0	0
Exposure, net of collateral	$ 0	$ 0