Investments (Unconsolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Carrying Amount Asset	$ 58,325	$ 55,832
Carrying Amount Liability	62,510	60,695
Other limited partnership interests
Variable Interest Entity [Line Items]
Carrying Amount Asset	4,657	4,714
Carrying Amount Liability	8,417	8,990
Other invested assets
Variable Interest Entity [Line Items]
Carrying Amount Asset	2,286	2,206
Carrying Amount Liability	2,697	2,777
Other
Variable Interest Entity [Line Items]
Carrying Amount Asset	114	199
Carrying Amount Liability	128	215
Structured securities (RMBS, CMBS, and ABS)
Variable Interest Entity [Line Items]
Carrying Amount Asset	49,663	46,773
Carrying Amount Liability	49,663	46,773
U.S. corporate and foreign corporate securities
Variable Interest Entity [Line Items]
Carrying Amount Asset	1,605	1,940
Carrying Amount Liability	$ 1,605	$ 1,940