Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental Cash Flow Information [Abstract]
Non-cash modifications of certain mortgage loans, fixed income securities, limited partnership interests and other investments, as well as mergers completed with equity securities	$ 5	$ 7
Non-cash financing activities related to the issuance of shares for vested restricted stock units	40	37
Debt acquired		34
Net change in proceeds managed
Net change in fixed income securities	(17)	0
Net change in short-term investments	(26)	(34)
Operating cash flow used	(43)	(34)
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(1,129)	(840)
Liabilities for collateral, end of period	(1,172)	(874)
Operating cash flow provided	$ 43	$ 34