Business, Basis of Presentation and Summary of Significant Accounting Policies - Transition Table SOE (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 25,895	$ 29,640	$ 34,009	$ 30,492	$ 34,009	$ 25,895	$ 29,640	$ 30,125	$ 50,013
Net income (loss)	495	1,167		493	2,554	988	3,721
Other Comprehensive Income (Loss), Net of Tax	(3,868)	(4,420)		2,219	(15,658)
Change in equity of noncontrolling interests		(19)		(8)	(9)
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		25,330	37,367		37,367		25,330	27,287	67,749
Net income (loss)		400					1,212
Revision of Prior Period, Accounting Standards Update, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest								2,838
Net income (loss)		767					2,509
Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		4,310	(3,358)		(3,358)		4,310	2,838	(17,736)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	39,958	39,176	38,478	39,928	38,478	39,958	39,176	40,332	36,831
Net income (loss)	489	1,162	2,544	482	2,544
Retained Earnings | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		41,032	41,101		41,101		41,032	41,953	41,197
Net income (loss)		395	801
Retained Earnings | Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(1,856)	(2,623)		(2,623)		(1,856)	(1,621)	(4,366)
Net income (loss)		767	1,743
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(24,254)	(22,526)	(18,106)	(20,386)	(18,106)	(24,254)	(22,526)	(22,621)	(2,451)
Other Comprehensive Income (Loss), Net of Tax	(3,868)	(4,420)	(15,655)	2,235	(15,655)
Accumulated Other Comprehensive Income (Loss) | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(28,695)	(17,372)		(17,372)		(28,695)	(27,083)	10,919
Other Comprehensive Income (Loss), Net of Tax		(11,323)	(28,291)
Accumulated Other Comprehensive Income (Loss) | Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		6,169	(734)		(734)		6,169	4,462	(13,370)
Other Comprehensive Income (Loss), Net of Tax		6,903	12,636
Total MetLife, Inc.'s Stockholders' Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	25,658	29,389	33,744	30,261	33,744	25,658	29,389	29,881	49,746
Net income (loss)	489	1,162		482	2,544
Other Comprehensive Income (Loss), Net of Tax	(3,868)	(4,420)		2,235	(15,655)
Change in equity of noncontrolling interests		0		0	0
Total MetLife, Inc.'s Stockholders' Equity | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		25,076	37,101		37,101		25,076	27,040	67,482
Total MetLife, Inc.'s Stockholders' Equity | Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		4,313	(3,357)		(3,357)		4,313	2,841	(17,736)
Noncontrolling Interests
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	237	251	265	231	265	$ 237	251	244	267
Net income (loss)	$ 6	5	10	11	10
Other Comprehensive Income (Loss), Net of Tax				(16)	(3)
Change in equity of noncontrolling interests		(19)		$ (8)	(9)
Noncontrolling Interests | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		254	266		266		254	247	267
Net income (loss)			11
Change in equity of noncontrolling interests		(17)
Noncontrolling Interests | Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(3)	(1)		$ (1)		$ (3)	$ (3)	$ 0
Net income (loss)			$ (1)
Change in equity of noncontrolling interests		$ (2)