Business, Basis of Presentation and Summary of Significant Accounting Policies - Transition Table SOE (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 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	$ 30,492	$ 32,423	$ 34,009	$ 42,703	$ 30,492	$ 34,009	$ 30,125	$ 50,013
Net income (loss)	408	85	915	1,639	493	2,554
Other Comprehensive Income (Loss), Net of Tax	(1,237)	3,456	(8,063)	(7,595)
Change in equity of noncontrolling interests	(6)	(2)	(10)	1
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			37,367	54,237		37,367	27,287	67,749
Net income (loss)			138			812
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)			777			1,742
Revision of Prior Period, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(3,358)	(11,534)		(3,358)	2,838	(17,736)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	39,928	39,957	38,478	38,005	39,928	38,478	40,332	36,831
Net income (loss)	402	80	910	1,634
Retained Earnings | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			41,101	41,406		41,101	41,953	41,197
Net income (loss)			132	669
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			(2,623)	(3,401)		(2,623)	(1,621)	(4,366)
Net income (loss)			778	965
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(20,386)	(19,147)	(18,106)	(10,044)	(20,386)	(18,106)	(22,621)	(2,451)
Other Comprehensive Income (Loss), Net of Tax	(1,239)	3,474	(8,062)	(7,593)
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			(17,372)	(1,912)		(17,372)	(27,083)	10,919
Other Comprehensive Income (Loss), Net of Tax			(15,460)	(12,831)
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			(734)	(8,132)		(734)	4,462	(13,370)
Other Comprehensive Income (Loss), Net of Tax			7,398	5,238
Total MetLife, Inc.'s Stockholders' Equity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	30,261	32,194	33,744	42,432	30,261	33,744	29,881	49,746
Net income (loss)	402	80	910	1,634
Other Comprehensive Income (Loss), Net of Tax	(1,239)	3,474	(8,062)	(7,593)
Change in equity of noncontrolling interests	0	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			37,101	53,965		37,101	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			(3,357)	(11,533)		(3,357)	2,841	(17,736)
Noncontrolling Interests
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	231	229	265	271	$ 231	265	244	267
Net income (loss)	6	5	5	5
Other Comprehensive Income (Loss), Net of Tax	2	(18)	(1)	(2)
Change in equity of noncontrolling interests	$ (6)	$ (2)	(10)	1
Noncontrolling Interests | Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			266	272		266	247	267
Net income (loss)			6	5
Other Comprehensive Income (Loss), Net of Tax				(2)
Change in equity of noncontrolling interests			(11)	2
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			(1)	(1)		$ (1)	$ (3)	$ 0
Net income (loss)			(1)	0
Other Comprehensive Income (Loss), Net of Tax				0
Change in equity of noncontrolling interests			$ 1	$ (1)