Investments (Schedule of Securities Pledged by Contractual Maturity) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Repurchase Agreements		$ 536	$ 535
Securities Lending	[1]	127	216
Total gross secured borrowings		663	751
Corporate bonds [Member]
Repurchase Agreements		536	535
Securities Lending		127	212
Foreign government bonds [Member]
Securities Lending			4
Overnight and Continuous [Member]
Securities Lending		127	216
Total gross secured borrowings		127	216
Overnight and Continuous [Member] | Corporate bonds [Member]
Securities Lending		127	212
Overnight and Continuous [Member] | Foreign government bonds [Member]
Securities Lending			4
30 to 90 Days [Member]
Repurchase Agreements		386	389
Total gross secured borrowings		386	389
30 to 90 Days [Member] | Corporate bonds [Member]
Repurchase Agreements		386	389
Greater than 90 days [Member]
Repurchase Agreements		150	146
Total gross secured borrowings		150	146
Greater than 90 days [Member] | Corporate bonds [Member]
Repurchase Agreements		$ 150	$ 146

[1] Our pledged securities under securities lending agreements are included in fixed maturity AFS securities on our Consolidated Balance Sheets. We generally obtain collateral in an amount equal to 102% and 105% of the fair value of the domestic and foreign securities, respectively. We value collateral daily and obtain additional collateral when deemed appropriate. The cash received in our securities lending program is typically invested in cash and invested cash or fixed maturity AFS securities.