Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Investment Income [Line Items]
Less: Investment expenses	$ 297	$ 296
Subtotal	5,196	4,559
Securities Investment
Net Investment Income [Line Items]
Subtotal	5,075	4,949
Subtotal	4,778	4,653
Fixed maturity securities
Net Investment Income [Line Items]
Subtotal	3,420	3,654
Equity securities
Net Investment Income [Line Items]
Subtotal	34	37
Actively traded securities and FVO general account securities
Net Investment Income [Line Items]
Subtotal	29	6
Mortgage loans
Net Investment Income [Line Items]
Subtotal	845	807
Policy loans
Net Investment Income [Line Items]
Subtotal	145	149
Real estate and real estate joint ventures
Net Investment Income [Line Items]
Subtotal	165	157
Other limited partnership interests
Net Investment Income [Line Items]
Subtotal	297	46
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Subtotal	59	40
Operating joint ventures
Net Investment Income [Line Items]
Subtotal	2	12
Other
Net Investment Income [Line Items]
Subtotal	79	41
Consolidated Securitization Entities And Fair Value Option Contractholder-Directed Unit-Linked
Net Investment Income [Line Items]
Subtotal	418	(94)
FVO contractholder-directed unit-linked investments
Net Investment Income [Line Items]
Subtotal	416	(97)
Commercial mortgage loans | Consolidated Securitization Entities
Net Investment Income [Line Items]
Subtotal	$ 2	$ 3