Investments (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Investment Income [Line Items]
Less: Investment expenses	$ 1,147	$ 1,209	$ 1,178
Subtotal	19,947	19,281	21,153
Securities Investment
Net Investment Income [Line Items]
Subtotal	20,132	20,210	21,015
Subtotal	18,985	19,001	19,837
Fixed Maturity Securities
Net Investment Income [Line Items]
Subtotal	14,313	14,235	14,868
Equity securities
Net Investment Income [Line Items]
Subtotal	140	144	133
FVO and trading securities — FVO general account and Actively traded securities (1)
Net Investment Income [Line Items]
Subtotal	37	21	103
Mortgage Loans
Net Investment Income [Line Items]
Subtotal	3,259	3,136	2,928
Policy loans
Net Investment Income [Line Items]
Subtotal	589	603	629
Real estate and real estate joint ventures
Net Investment Income [Line Items]
Subtotal	684	981	951
Other limited partnership interests
Net Investment Income [Line Items]
Subtotal	641	669	1,033
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Subtotal	173	148	168
Operating joint ventures
Net Investment Income [Line Items]
Subtotal	33	25	10
Other
Net Investment Income [Line Items]
Subtotal	263	248	192
Consolidated Securitization Entities And Fair Value Option Contractholder-Directed Unit-Linked
Net Investment Income [Line Items]
Subtotal	962	280	1,316
FVO contractholder-directed unit-linked investments
Net Investment Income [Line Items]
Subtotal	950	264	1,266
Changes in estimated fair value included in net investment income	427	(456)	642
Commercial mortgage loans | Consolidated Securitization Entities
Net Investment Income [Line Items]
Subtotal	12	16	49
Securities | Consolidated Securitization Entities
Net Investment Income [Line Items]
Subtotal	$ 0	$ 0	$ 1