Derivative Financial Instruments (Details 4) $ in Millions	Sep. 30, 2017 USD ($) party	Dec. 31, 2016 USD ($) party
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash and securities pledged as collateral by counterparties	$ 3
Securities pledged as collateral to counterparties	5
Collateral already posted, aggregate fair value	3	$ 0
Collateral already posted, without credit-risk-contingent features	2
Credit Derivatives
Gross liability fair value of contracts containing credit-risk-contingent features	6	2
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(1)	(2)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 2	$ 0
A+
Credit Derivatives
Number of counter-parties (in Party) | party	3	5
Notional amount	$ 244	$ 312
Credit exposure	3	12
Exposure, net of collateral	$ 3	$ 9