Closed Block (Liabilities and Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Closed Block Liabilities
Future policy benefits	$ 40,654	$ 40,834
Other policy-related balances	223	257
Policyholder dividends payable	470	443
Policyholder dividend obligation	1,983	1,931	$ 1,783
Current income tax payable	11	4
Other liabilities	245	196
Total closed block liabilities	43,586	43,665
Assets Designated to the Closed Block
Fixed maturity securities available-for-sale, at estimated fair value	27,554	27,220
Equity securities available-for-sale, at estimated fair value	102	100
Mortgage loans	5,857	5,935
Policy loans	4,550	4,553
Real estate and real estate joint ventures	654	655
Other invested assets	904	1,246
Total investments	39,621	39,709
Cash and cash equivalents	46	18
Accrued investment income	483	467
Premiums, reinsurance and other receivables	62	68
Deferred income tax assets	171	177
Total assets designated to the closed block	40,383	40,439
Excess of closed block liabilities over assets designated to the closed block	3,203	3,226
Amounts included in accumulated other comprehensive income (loss) (“AOCI”):
Unrealized investment gains (losses), net of income tax	1,582	1,517
Unrealized gains (losses) on derivatives, net of income tax	85	95
Allocated to policyholder dividend obligation, net of income tax	(1,289)	(1,255)
Total amounts included in AOCI	378	357
Maximum future earnings to be recognized from closed block assets and liabilities	$ 3,581	$ 3,583