Earnings Per Common Share (Details) (USD $) In Millions, except 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
Weighted Average Shares:
Weighted average common stock outstanding for basic earnings per common share									1,070,755,561	1,059,580,442	882,436,532
Incremental common shares from assumed:
Stock purchase contracts underlying common equity units									0	1,641,444	0
Exercise or issuance of stock-based awards									6,084,078	6,872,474	7,131,346
Weighted average common stock outstanding for diluted earnings per common share									1,076,839,639	1,068,094,360	889,567,878
Income (Loss) from Continuing Operations:
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
Less: Income (loss) from continuing operations, net of income tax, attributable to noncontrolling interests									38	(8)	(4)
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
Income (loss) from continuing operations, net of income tax, available to MetLife, Inc.'s common shareholders									1,154	6,131	2,501
Basic	$ 0.06	$ (0.92)	$ 2.13	$ (0.17)	$ 0.88	$ 3.22	$ 0.98	$ 0.70	$ 1.08	$ 5.79	$ 2.83
Diluted	$ 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:
Income (loss) from discontinued operations, net of income tax	31	0	3	14	25	8	31	(40)	48	24	44
Less: Income (loss) from discontinued operations, net of income tax, attributable to noncontrolling interests									0	0	0
Income (loss) from discontinued operations, net of income tax, available to MetLife, Inc.'s common shareholders									48	24	44
Basic	$ 0.03	$ 0.00	$ 0.00	$ 0.01	$ 0.02	$ 0.01	$ 0.03	$ (0.04)	$ 0.04	$ 0.02	$ 0.05
Diluted	$ 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):
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)
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	$ 0.09	$ (0.92)	$ 2.13	$ (0.16)	$ 0.90	$ 3.23	$ 1.01	$ 0.66	$ 1.12	$ 5.81	$ 2.88
Diluted	$ 0.09	$ (0.92)	$ 2.12	$ (0.16)	$ 0.90	$ 3.21	$ 1.00	$ 0.66	$ 1.12	$ 5.76	$ 2.86