Investments (Changes in Net Unrealized Investment Gains Losses) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance, beginning of period	$ 12,631
Fixed maturity securities on which noncredit OTTI losses have been recognized	29
Unrealized investment gains (losses) during the period	503
Unrealized investment gains (losses) relating to:
Future policy benefits	1,051
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	2
DAC, VOBA and DSI	(217)
Policyholder dividend obligation	(270)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	(10)
Deferred income tax benefit (expense)	(374)
Net unrealized investment gains (losses)	13,345
Net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Balance, end of period	13,343
Change in net unrealized investment gains (losses)	714
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 712