Closed Block (Liabilities and Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Closed Block Liabilities
Future policy benefits	$ 40,463	$ 40,834
Other policy-related balances	222	257
Policyholder dividends payable	437	443
Policyholder dividend obligation	2,121	1,931	$ 1,783	$ 3,155
Current income tax payable	0	4
Other liabilities	212	196
Total closed block liabilities	43,455	43,665
Assets Designated to the Closed Block
Fixed maturity securities available-for-sale, at estimated fair value	27,904	27,220
Equity securities available-for-sale, at estimated fair value	70	100
Mortgage loans	5,878	5,935
Policy loans	4,548	4,553
Real estate and real estate joint ventures	613	655
Other invested assets	731	1,246
Total investments	39,744	39,709
Accrued investment income	477	467
Premiums, reinsurance and other receivables; cash and cash equivalents	14	86
Current income tax recoverable	35	0
Deferred income tax assets	36	177
Total assets designated to the closed block	40,306	40,439
Excess of closed block liabilities over assets designated to the closed block	3,149	3,226
Amounts included in AOCI:
Unrealized investment gains (losses), net of income tax	1,863	1,517
Unrealized gains (losses) on derivatives, net of income tax	(7)	95
Allocated to policyholder dividend obligation, net of income tax	(1,379)	(1,255)
Total amounts included in AOCI	477	357
Maximum future earnings to be recognized from closed block assets and liabilities	$ 3,626	$ 3,583