Closed Block (Liabilities and Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Closed Block Liabilities
Future policy benefits	$ 41,046	$ 41,278
Other policy-related balances	270	249
Policyholder dividends payable	484	468
Policyholder dividend obligation	2,586	1,783	$ 3,155
Other liabilities	799	380
Total closed block liabilities	45,185	44,158
Assets Designated to the Closed Block
Fixed maturity securities available-for-sale, at estimated fair value	28,739	27,556
Equity securities available-for-sale, at estimated fair value	108	111
Mortgage loans	5,910	6,022
Policy loans	4,561	4,642
Real estate and real estate joint ventures	458	462
Other invested assets	978	1,066
Total investments	40,754	39,859
Cash and cash equivalents	151	236
Accrued investment income	477	474
Premiums, reinsurance and other receivables	321	56
Current income tax recoverable	7	11
Deferred income tax assets	215	234
Total assets designated to the closed block	41,925	40,870
Excess of closed block liabilities over assets designated to the closed block	3,260	3,288
Amounts included in accumulated other comprehensive income (loss) (“AOCI”)
Unrealized investment gains (losses), net of income tax	1,963	1,382
Unrealized gains (losses) on derivatives, net of income tax	63	76
Allocated to policyholder dividend obligation, net of income tax	(1,681)	(1,159)
Total amounts included in AOCI	345	299
Maximum future earnings to be recognized from closed block assets and liabilities	$ 3,605	$ 3,587