Business, Basis of Presentation and Summary of Significant Accounting Policies - Transition Table - Income Statement (Details) - USD ($) $ / shares in Units, $ 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
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums	$ 11,678		$ 11,556		$ 21,267	$ 22,173
Universal life and investment-type product policy fees	1,288		1,372		2,577	2,684
Other revenues	621		615		1,260	1,275
Net investment gains (losses)	(1,039)		(682)		(1,723)	(1,199)
Net derivative gains (losses)	(997)		(970)		(1,087)	(1,921)
Total revenues	16,623		15,474		32,011	30,879
Policyholder benefits and claims	11,809		11,615		21,681	22,789
Policyholder liability remeasurement (gains) losses	(16)		(1)		(25)	(42)
Market risk benefit remeasurement (gains) losses	(817)		(757)		(629)	(2,197)
Interest credited to policyholder account balances	1,933		527		3,797	1,153
Policyholder dividends	151		194		310	393
Other expenses	3,133		2,908		6,190	5,860
Total expenses	16,193		14,486		31,324	27,956
Income (loss) before provision for income tax	430		988		687	2,923
Provision for income tax expense (benefit)	22		73		194	369
Net income (loss)	408	$ 85	915	$ 1,639	493	2,554
Net Income (Loss) Attributable to Noncontrolling Interest	6		5		11	10
Net income (loss) attributable to MetLife, Inc.	402		910		482	2,544
Net income (loss) available to MetLife, Inc.’s common shareholders	370		881		384	2,452
Comprehensive income (loss)	(829)		(7,148)		2,712	(13,104)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	8		4		(5)	7
Comprehensive income (loss) attributable to MetLife, Inc.	$ (837)		$ (7,152)		$ 2,717	$ (13,111)
Basic	$ 0.48		$ 1.09		$ 0.50	$ 3.00
Diluted	$ 0.48		$ 1.08		$ 0.50	$ 2.98
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums			$ 11,721			$ 22,492
Universal life and investment-type product policy fees			1,516			2,934
Other revenues			616			1,276
Net investment gains (losses)			(685)			(1,203)
Net derivative gains (losses)			(1,195)			(2,054)
Total revenues			15,556			31,312
Policyholder benefits and claims			11,790			22,983
Policyholder liability remeasurement (gains) losses			0			0
Market risk benefit remeasurement (gains) losses			0			0
Interest credited to policyholder account balances			492			1,122
Policyholder dividends			193			391
Other expenses			3,083			6,103
Total expenses			15,558			30,599
Income (loss) before provision for income tax			(2)			713
Provision for income tax expense (benefit)			(140)			(99)
Net income (loss)			138			812
Net Income (Loss) Attributable to Noncontrolling Interest			6			11
Net income (loss) attributable to MetLife, Inc.			132			801
Net income (loss) available to MetLife, Inc.’s common shareholders			103			709
Comprehensive income (loss)			(15,323)			(27,482)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			5			8
Comprehensive income (loss) attributable to MetLife, Inc.			$ (15,328)			$ (27,490)
Basic			$ 0.13			$ 0.87
Diluted			$ 0.13			$ 0.86
Revision of Prior Period, Accounting Standards Update, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums			$ (165)			$ (319)
Universal life and investment-type product policy fees			(144)			(250)
Other revenues			(1)			(1)
Net investment gains (losses)			3			4
Net derivative gains (losses)			225			133
Total revenues			(82)			(433)
Policyholder benefits and claims			(175)			(194)
Policyholder liability remeasurement (gains) losses			(1)			(42)
Market risk benefit remeasurement (gains) losses			(757)			(2,197)
Interest credited to policyholder account balances			35			31
Policyholder dividends			1			2
Other expenses			(175)			(243)
Total expenses			(1,072)			(2,643)
Income (loss) before provision for income tax			990			2,210
Provision for income tax expense (benefit)			213			468
Net income (loss)			777			1,742
Net Income (Loss) Attributable to Noncontrolling Interest			(1)			(1)
Net income (loss) attributable to MetLife, Inc.			778			1,743
Net income (loss) available to MetLife, Inc.’s common shareholders			778			1,743
Comprehensive income (loss)			8,175			14,378
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			(1)			(1)
Comprehensive income (loss) attributable to MetLife, Inc.			$ 8,176			$ 14,379
Basic			$ 0.96			$ 2.13
Diluted			$ 0.95			$ 2.12