Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 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	$ 31	$ 290
Non-cash financing activities related to the issuance of shares for vested restricted stock units	42	40
Debt acquired		34
Net change in proceeds managed
Net change in fixed income securities	129	(436)
Net change in short-term investments	(157)	181
Operating cash flow used	(28)	(255)
Net change in cash	1	0
Net change in proceeds managed	(27)	(255)
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(1,129)	(840)
Liabilities for collateral, end of period	(1,156)	(1,095)
Operating cash flow provided	$ 27	$ 255