Condensed Financial Information (Parent Company) (Condensed Statements of Operations) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Net Investment Income									$ 16,166	$ 17,363	$ 16,790
Other revenues									1,880	1,341	1,685
Net investment gains (losses)									(298)	(308)	317
Net derivative gains (losses)									851	(590)	(690)
Total revenues	$ 15,662	$ 16,289	$ 21,185	$ 14,805	$ 15,840	$ 16,171	$ 15,333	$ 14,964	67,941	62,308	60,787
Expenses
Goodwill impairment									0	0	260
Other expenses									13,714	13,621	13,749
Total expenses	13,191	15,210	20,084	13,149	14,879	15,686	14,315	13,892	61,634	58,772	56,506
Income (loss) from before provision for income tax									6,307	3,536	4,281
Provision for income tax expense (benefit)									1,179	(1,470)	693
Net income (loss)	2,067	912	891	1,253	2,317	(91)	911	873	5,123	4,010	850
Less: Preferred stock dividends	57	32	46	6	45	6	46	6	141	103	103
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 2,010	$ 880	$ 845	$ 1,247	$ 2,272	$ (97)	$ 865	$ 867	4,982	3,907	747
Comprehensive income (loss)									(1,494)	7,391	1,449
Parent Company
Condensed Income Statements, Captions [Line Items]
Equity in earnings of subsidiaries									6,466	7,162	1,833
Net Investment Income									87	101	129
Other revenues									19	59	151
Net investment gains (losses)									(277)	(1,142)	86
Net derivative gains (losses)									(56)	(186)	(68)
Total revenues									6,239	5,994	2,131
Expenses
Interest expense									1,009	1,108	1,152
Goodwill impairment									0	0	147
Other expenses									158	657	388
Total expenses									1,167	2,059	1,689
Income (loss) from before provision for income tax									5,072	3,935	442
Provision for income tax expense (benefit)									(51)	(75)	(408)
Net income (loss)									5,123	4,010	850
Less: Preferred stock dividends									141	103	103
Net income (loss) available to MetLife, Inc.’s common shareholders									4,982	3,907	747
Comprehensive income (loss)									(1,494)	7,391	1,449
Brighthouse Financial, Inc
Condensed Income Statements, Captions [Line Items]
Other revenues									305
Net investment gains (losses)										(1,016)
Expenses
Goodwill impairment											260
Other expenses										(18)	59
Brighthouse Financial, Inc | Parent Company
Expenses
Termination of financing arrangements									$ 0	$ 294	$ 2