Investments (Unconsolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Proceeds From Securitizations of Loans Held-for-Investment, Carry Value	$ 451
Carrying Amount Asset	55,798	$ 56,381
Carrying Amount Liability	60,356	60,429
Proceeds from Securitizations of Loans Held-for-investment	478
Gain (Loss) on Securitization of Financial Assets	27
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds In Period	102
Other limited partnership interests
Variable Interest Entity [Line Items]
Carrying Amount Asset	5,343	4,834
Carrying Amount Liability	9,719	8,543
Other invested assets
Variable Interest Entity [Line Items]
Carrying Amount Asset	1,924	2,291
Carrying Amount Liability	2,102	2,625
Other
Variable Interest Entity [Line Items]
Carrying Amount Asset	86	82
Carrying Amount Liability	90	87
Structured securities (RMBS, CMBS, and ABS)
Variable Interest Entity [Line Items]
Carrying Amount Asset	47,209	47,614
Carrying Amount Liability	47,209	47,614
U.S. corporate and foreign corporate securities
Variable Interest Entity [Line Items]
Carrying Amount Asset	1,236	1,560
Carrying Amount Liability	$ 1,236	$ 1,560