Investments (Net Unrealized Investment Gains Losses) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities that were temporarily impaired	$ 26,848	$ 16,672
Fixed maturity securities with noncredit OTTI losses in accumulated other comprehensive income (loss)	(105)	(218)	(361)
Total fixed maturity securities	26,743	16,454
Equity securities	602	390
Derivatives	1,326	375
Other	24	(73)
Subtotal	28,695	17,146
Insurance liability loss recognition	(1,515)	(898)
DAC and VOBA related to noncredit OTTI losses recognized in accumulated other comprehensive income (loss)	2	6
DAC and VOBA	(1,866)	(1,190)
Policyholder dividend obligation	(2,825)	(1,771)
Subtotal	(6,204)	(3,853)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in accumulated other comprehensive income (loss)	33	73
Deferred income tax benefit (expense)	(7,835)	(4,956)
Net unrealized investment gains (losses)	14,689	8,410
Net unrealized investment gains (losses) attributable to noncontrolling interests	0	4
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 14,689	$ 8,414