Business, Basis of Presentation and Summary of Significant Accounting Policies - Transition Table - Income Statement (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums	$ 9,589	$ 10,617
Universal life and investment-type product policy fees	1,289	1,312
Net investment gains (losses)	(684)	(517)
Net derivative gains (losses)	(90)	(951)
Total revenues	15,388	15,405
Policyholder benefits and claims	9,872	11,174
Policyholder liability remeasurement (gains) losses	(9)	(41)
Market risk benefit remeasurement (gains) losses	188	(1,440)
Interest credited to policyholder account balances	1,864	626
Policyholder dividends	159	199
Other expenses	3,057	2,952
Total expenses	15,131	13,470
Income (loss) before provision for income tax	257	1,935
Provision for income tax expense (benefit)	172	296
Net income (loss)	85	1,639
Net income (loss) attributable to MetLife, Inc.	80	1,634
Net income (loss) available to MetLife, Inc.’s common shareholders	14	1,571
Comprehensive income (loss)	3,541	(5,956)
Comprehensive income (loss) attributable to MetLife, Inc.	$ 3,554	$ (5,959)
Basic	$ 0.02	$ 1.91
Diluted	$ 0.02	$ 1.89
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums		$ 10,771
Universal life and investment-type product policy fees		1,418
Net investment gains (losses)		(518)
Net derivative gains (losses)		(859)
Total revenues		15,756
Policyholder benefits and claims		11,193
Policyholder liability remeasurement (gains) losses		0
Market risk benefit remeasurement (gains) losses		0
Interest credited to policyholder account balances		630
Policyholder dividends		198
Other expenses		3,020
Total expenses		15,041
Income (loss) before provision for income tax		715
Provision for income tax expense (benefit)		41
Net income (loss)		674
Net income (loss) attributable to MetLife, Inc.		669
Net income (loss) available to MetLife, Inc.’s common shareholders		606
Comprehensive income (loss)		(12,159)
Comprehensive income (loss) attributable to MetLife, Inc.		$ (12,162)
Basic		$ 0.74
Diluted		$ 0.73
Revision of Prior Period, Accounting Standards Update, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums		$ (154)
Universal life and investment-type product policy fees		(106)
Net investment gains (losses)		1
Net derivative gains (losses)		(92)
Total revenues		(351)
Policyholder benefits and claims		(19)
Policyholder liability remeasurement (gains) losses		(41)
Market risk benefit remeasurement (gains) losses		(1,440)
Interest credited to policyholder account balances		(4)
Policyholder dividends		1
Other expenses		(68)
Total expenses		(1,571)
Income (loss) before provision for income tax		1,220
Provision for income tax expense (benefit)		255
Net income (loss)		965
Net income (loss) attributable to MetLife, Inc.		965
Net income (loss) available to MetLife, Inc.’s common shareholders		965
Comprehensive income (loss)		6,203
Comprehensive income (loss) attributable to MetLife, Inc.		$ 6,203
Basic		$ 1.17
Diluted		$ 1.16