Business, Basis of Presentation and Summary of Significant Accounting Policies - Transition Table - SOE (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 30,253				$ 30,125				$ 30,253	$ 30,125	$ 50,013	$ 74,817
Net income (loss)	614	$ 495	$ 408	$ 85	1,581	$ 1,167	$ 915	$ 1,639	1,602	5,302	6,876
Other Comprehensive Income (Loss), Net of Tax									3,361	(20,177)	(2,763)
Change in equity of noncontrolling interests									(12)	(34)	(16)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(22,424)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	40,146				40,332				40,146	40,332	36,831	36,491
Net income (loss)									1,578	5,284	6,855	6,855
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(4,667)
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(19,242)				(22,621)				(19,242)	(22,621)	(2,451)	18,072	$ 315
Other Comprehensive Income (Loss), Net of Tax									3,379	(20,170)	(2,766)	(2,766)
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(17,757)
Total MetLife, Inc.'s Stockholders' Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	30,015				29,881				30,015	29,881	49,746	74,558
Net income (loss)									1,578	5,284	6,855
Other Comprehensive Income (Loss), Net of Tax									3,379	(20,170)	(2,766)
Change in equity of noncontrolling interests									0	0	0
Total MetLife, Inc.'s Stockholders' Equity | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(22,424)
Noncontrolling Interests
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 238				244				238	244	267	259
Net income (loss)									24	18	21
Other Comprehensive Income (Loss), Net of Tax									(18)	(7)	3
Change in equity of noncontrolling interests									$ (12)	(34)	(16)
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					27,287					27,287	67,749	74,817
Net income (loss)										2,558	6,575
Other Comprehensive Income (Loss), Net of Tax										(38,008)	(7,150)
Change in equity of noncontrolling interests										(33)
Previously Reported | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												0
Previously Reported | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					41,953					41,953	41,197	36,491
Net income (loss)										2,539		6,554
Previously Reported | Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												0
Previously Reported | Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					(27,083)					(27,083)	10,919	18,072
Other Comprehensive Income (Loss), Net of Tax										(38,002)		(7,153)
Previously Reported | Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												0
Previously Reported | Total MetLife, Inc.'s Stockholders' Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					27,040					27,040	67,482	74,558
Net income (loss)										2,539	6,554
Other Comprehensive Income (Loss), Net of Tax										(38,002)	(7,153)
Previously Reported | Total MetLife, Inc.'s Stockholders' Equity | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												0
Previously Reported | Noncontrolling Interests
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					247					247	267
Net income (loss)										19
Other Comprehensive Income (Loss), Net of Tax										(6)
Change in equity of noncontrolling interests										(33)
Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					2,838					2,838	(17,736)	0
Net income (loss)										2,744	301
Other Comprehensive Income (Loss), Net of Tax										17,831	4,387
Change in equity of noncontrolling interests										(1)
Restatement Adjustment | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(22,424)
Restatement Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					(1,621)					(1,621)	(4,366)	0
Net income (loss)										2,745		301
Restatement Adjustment | Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(4,667)
Restatement Adjustment | Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					4,462					4,462	(13,370)	0
Other Comprehensive Income (Loss), Net of Tax										17,832		4,387
Restatement Adjustment | Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												(17,757)
Restatement Adjustment | Total MetLife, Inc.'s Stockholders' Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					2,841					2,841	(17,736)	0
Net income (loss)										2,745	301
Other Comprehensive Income (Loss), Net of Tax										17,832	4,387
Restatement Adjustment | Total MetLife, Inc.'s Stockholders' Equity | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest												$ (22,424)
Restatement Adjustment | Noncontrolling Interests
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					$ (3)					(3)	$ 0
Net income (loss)										(1)
Other Comprehensive Income (Loss), Net of Tax										(1)
Change in equity of noncontrolling interests										$ (1)