Quarterly Results of Operations (Unaudited) (Quarterly Results of Operations) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Results of Operations (Unaudited)
Total revenues	$ 12,076	$ 17,723	$ 15,244	$ 18,433	$ 17,044	$ 18,031	$ 16,166	$ 18,710	$ 63,476	$ 69,951	$ 73,316
Total expenses	15,641	17,175	15,344	15,511	15,909	15,868	15,053	15,651	63,671	62,481	64,512
Income (loss) from continuing operations, net of income tax	(2,086)	573	114	2,203	842	1,198	1,119	2,163	804	5,322	6,339
Income (loss) from discontinued operations, net of income tax	0	0	0	0	0	0	0	0	0	0	(3)
Net income (loss)	(2,086)	573	114	2,203	842	1,198	1,119	2,163	804	5,322	6,336
Less: Net income (loss) attributable to noncontrolling interests	2	(4)	4	2	8	(5)	4	5	4	12	27
Net income (loss) attributable to MetLife, Inc.	(2,088)	577	110	2,201	834	1,203	1,115	2,158	800	5,310	6,309
Less: Preferred stock dividends	45	6	46	6	49	6	31	30	103	116	122
Preferred stock repurchase premium	0	0	0	0	0	0	42	0	0	42	0
Net income (loss) available to MetLife, Inc.’s common shareholders	$ (2,133)	$ 571	$ 64	$ 2,195	$ 785	$ 1,197	$ 1,042	$ 2,128	$ 697	$ 5,152	$ 6,187
Basic earnings per common share
Income (loss) from continuing operations, net of income tax, available to MetLife, Inc.’s common shareholders	$ (1.94)	$ 0.52	$ 0.06	$ 1.99	$ 0.71	$ 1.07	$ 0.93	$ 1.89	$ 0.63	$ 4.61	$ 5.48
Income (loss) from discontinued operations, net of income tax, attributable to MetLife, Inc.	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Net income (loss) attributable to MetLife, Inc.	(1.90)	0.52	0.10	2.00	0.75	1.08	1.00	1.92
Net income (loss) available to MetLife, Inc.’s common shareholders	(1.94)	0.52	0.06	1.99	0.71	1.07	0.93	1.89	0.63	4.61	5.48
Diluted earnings per common share (1)
Income (loss) from continuing operations, net of income tax, available to MetLife, Inc.’s common shareholders	(1.94)	0.51	0.06	1.98	0.70	1.06	0.92	1.87	0.63	4.57	5.42
Income (loss) from discontinued operations, net of income tax, attributable to MetLife, Inc.	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Net income (loss) attributable to MetLife, Inc.	(1.90)	0.52	0.10	1.99	0.74	1.06	0.99	1.90
Net income (loss) available to MetLife, Inc.’s common shareholders	$ (1.94)	$ 0.51	$ 0.06	$ 1.98	$ 0.70	$ 1.06	$ 0.92	$ 1.87	$ 0.63	$ 4.57	$ 5.42
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	9,200,000.0								8,000,000.0	10,500,000.0	10,900,000.0