Quarterly Results of Operations (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results of Operations (Unaudited)
Total revenues	$ 17,333	$ 16,503	$ 18,398	$ 15,916	$ 16,735	$ 20,453	$ 17,146	$ 15,907	$ 68,150	$ 70,241	$ 52,247
Total expenses	17,810	17,513	15,060	16,325	15,460	15,338	15,636	14,623	66,708	61,057	48,518
Income (loss) from continuing operations, net of income tax	105	(957)	2,300	(134)	963	3,442	1,062	924	1,314	6,391	2,619
Income (loss) from discontinued operations, net of income tax	31	0	3	14	25	8	31	(40)	48	24	44
Net income (loss)	136	(957)	2,303	(120)	988	3,450	1,093	884	1,362	6,415	2,663
Less: Net income (loss) attributable to noncontrolling interests	9	(3)	8	24	(2)	(6)	(7)	7	38	(8)	(4)
Net income (loss) attributable to MetLife, Inc.	127	(954)	2,295	(144)	990	3,456	1,100	877	1,324	6,423	2,667
Less: Preferred stock dividends	31	30	31	30	31	30	31	30	122	122	122
Preferred stock redemption premium	0	0	0	0	0	0	0	146	0	146	0
Net income (loss) available to MetLife, Inc.'s common shareholders	$ 96	$ (984)	$ 2,264	$ (174)	$ 959	$ 3,426	$ 1,069	$ 701	$ 1,202	$ 6,155	$ 2,545
Basic earnings per common share:
Income (loss) from continuing operations, net of income tax, available to MetLife, Inc.'s common shareholders	$ 0.06	$ (0.92)	$ 2.13	$ (0.17)	$ 0.88	$ 3.22	$ 0.98	$ 0.70	$ 1.08	$ 5.79	$ 2.83
Income (loss) from discontinued operations, net of income tax, attributable to MetLife, Inc.	$ 0.03	$ 0.00	$ 0.00	$ 0.01	$ 0.02	$ 0.01	$ 0.03	$ (0.04)	$ 0.04	$ 0.02	$ 0.05
Net income (loss) attributable to MetLife, Inc.	$ 0.12	$ (0.90)	$ 2.16	$ (0.14)	$ 0.93	$ 3.26	$ 1.04	$ 0.83
Net income (loss) available to MetLife, Inc.'s common shareholders	$ 0.09	$ (0.92)	$ 2.13	$ (0.16)	$ 0.90	$ 3.23	$ 1.01	$ 0.66	$ 1.12	$ 5.81	$ 2.88
Diluted earnings per common share:
Income (loss) from continuing operations, net of income tax, available to MetLife, Inc.'s common shareholders	$ 0.06	$ (0.92)	$ 2.12	$ (0.17)	$ 0.88	$ 3.20	$ 0.97	$ 0.70	$ 1.08	$ 5.74	$ 2.81
Income (loss) from discontinued operations, net of income tax, attributable to MetLife, Inc.	$ 0.03	$ 0.00	$ 0.00	$ 0.01	$ 0.02	$ 0.01	$ 0.03	$ (0.04)	$ 0.04	$ 0.02	$ 0.05
Net income (loss) attributable to MetLife, Inc.	$ 0.12	$ (0.90)	$ 2.14	$ (0.14)	$ 0.93	$ 3.24	$ 1.03	$ 0.82
Net income (loss) available to MetLife, Inc.'s common shareholders	$ 0.09	$ (0.92)	$ 2.12	$ (0.16)	$ 0.90	$ 3.21	$ 1.00	$ 0.66	$ 1.12	$ 5.76	$ 2.86