Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net Investment Income [Line Items]
Less: Investment expenses	$ 310	$ 285	$ 607	$ 581
Subtotal	4,959	4,887	10,155	9,446
Securities Investment
Net Investment Income [Line Items]
Subtotal	5,053	4,979	10,128	9,928
Subtotal	4,743	4,694	9,521	9,347
Fixed maturity securities
Net Investment Income [Line Items]
Subtotal	3,431	3,564	6,851	7,218
Equity securities
Net Investment Income [Line Items]
Subtotal	35	33	69	70
Actively traded securities and FVO general account securities
Net Investment Income [Line Items]
Subtotal	16	10	45	16
Mortgage loans
Net Investment Income [Line Items]
Subtotal	869	851	1,714	1,658
Policy loans
Net Investment Income [Line Items]
Subtotal	146	147	291	296
Real estate and real estate joint ventures
Net Investment Income [Line Items]
Subtotal	184	149	349	306
Other limited partnership interests
Net Investment Income [Line Items]
Subtotal	243	120	540	166
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Subtotal	67	43	126	83
Operating joint ventures
Net Investment Income [Line Items]
Subtotal	5	11	7	23
Other
Net Investment Income [Line Items]
Subtotal	57	51	136	92
Consolidated Securitization Entities And Fair Value Option Contractholder-Directed Unit-Linked
Net Investment Income [Line Items]
Subtotal	216	193	634	99
FVO contractholder-directed unit-linked investments
Net Investment Income [Line Items]
Subtotal	214	191	630	94
Commercial mortgage loans | Consolidated Securitization Entities
Net Investment Income [Line Items]
Subtotal	$ 2	$ 2	$ 4	$ 5