Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities	$ 28,427	$ 18,164
Fixed maturity securities with noncredit OTTI losses included in AOCI	(91)	(76)	$ (112)
Total fixed maturity securities	28,336	18,088
Equity securities	447	422
Derivatives	2,723	2,350
Other	359	287
Subtotal	31,865	21,147
Future policy benefits	(1,415)	(163)
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	2	0
DAC, VOBA and DSI	(1,900)	(1,273)
Policyholder dividend obligation	(2,586)	(1,783)
Subtotal	(5,899)	(3,219)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	39	27
Deferred income tax benefit (expense)	(8,825)	(6,151)
Net unrealized investment gains (losses)	17,180	11,804
Net unrealized investment gains (losses) attributable to noncontrolling interests	(9)	(31)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 17,171	$ 11,773