Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 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	$ 9	$ 270
Non-cash financing activities related to the issuance of shares for vested restricted stock units	42	39
Debt acquired		34
Net change in proceeds managed
Net change in fixed income securities	10	0
Net change in short-term investments	(7)	(56)
Operating cash flow provided (used)	3	(56)
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(1,129)	(840)
Liabilities for collateral, end of period	(1,126)	(896)
Operating cash flow (used) provided	$ (3)	$ 56