Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities	$ 36,633	$ 18,164
Fixed maturity securities with noncredit OTTI losses included in AOCI	(59)	(76)	$ (112)
Total fixed maturity securities	36,574	18,088
Equity securities	558	422
Derivatives	3,766	2,350
Other	333	287
Subtotal	41,231	21,147
Future policy benefits	(4,410)	(163)
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	(2)	0
DAC, VOBA and DSI	(2,380)	(1,273)
Policyholder dividend obligation	(3,343)	(1,783)
Subtotal	(10,135)	(3,219)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	23	27
Deferred income tax benefit (expense)	(10,473)	(6,151)
Net unrealized investment gains (losses)	20,646	11,804
Net unrealized investment gains (losses) attributable to noncontrolling interests	(11)	(31)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 20,635	$ 11,773