Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Non-cash modifications of certain mortgage loans, fixed income securities, limited partnership interests and other investments, as well as mergers completed with equity securities	$ 326	$ 131	$ 120
Liabilities assumed	34
Non-cash financing activities related to the issuance of shares for vested restricted stock units	41	74	47
Liabilities for collateral received reported in other liabilities and accrued expenses	1,120	829	780
Obligations to return cash collateral for over-the-counter ("OTC") and cleared derivatives reported in other liabilities and accrued expenses or other investments	5	11	2
Net change in proceeds managed
Net change in fixed income securities	(584)	0	0
Net change in short-term investments	295	(59)	(167)
Operating cash flow used	(289)	(59)	(167)
Net change in cash	0	1	9
Net change in proceeds managed	(289)	(58)	(158)
Net change in liabilities
Liabilities for collateral, beginning of year	(840)	(782)	(624)
Liabilities for collateral, end of year	(1,129)	(840)	(782)
Operating cash flow provided	$ 289	58	$ 158
Limited Partnership
Debt Instrument [Line Items]
Liabilities assumed		$ 89