Business, Basis of Presentation and Summary of Significant Accounting Policies - Transition Table - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums, reinsurance and other receivables	$ 28,971	$ 17,364		$ 18,169
Asset	286	280
Deferred policy acquisition costs and value of business acquired	20,151	19,653	$ 19,806	20,417
Deferred income tax asset	2,612	2,439
Other assets	11,139	11,025		11,742
Total Assets	687,584	663,072
Future policy benefits	196,406	187,222		224,358
Policyholder account balance	219,269	210,597		211,737
Liability	3,179	3,763		7,901
Other Policy-Related Balances	19,736	18,424		18,032
Deferred income tax liability	927	950		4,723
Other liabilities	35,805	25,933
Total Liabilities	657,331	632,947
Retained earnings	40,146	40,332		31,824
Accumulated other comprehensive income (loss)	(19,242)	(22,621)		$ 315
Total MetLife, Inc.’s stockholders’ equity	30,015	29,881
Noncontrolling interests	238	244
Total equity	30,253	30,125	50,013		$ 74,817
Total liabilities and equity	$ 687,584	663,072
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums, reinsurance and other receivables		17,461			17,870
Asset		0
Deferred policy acquisition costs and value of business acquired		22,983			16,389
Deferred income tax asset		2,830
Other assets		11,026			11,685
Total Assets		666,611
Future policy benefits		204,228			206,656
Policyholder account balance		203,082			205,176
Liability		0			0
Other Policy-Related Balances		19,651			17,101
Deferred income tax liability		325			11,008
Other liabilities		25,980
Total Liabilities		639,324
Retained earnings		41,953			36,491
Accumulated other comprehensive income (loss)		(27,083)			18,072
Total MetLife, Inc.’s stockholders’ equity		27,040
Noncontrolling interests		247
Total equity		27,287	$ 67,749		$ 74,817
Total liabilities and equity		666,611
Revision of Prior Period, Accounting Standards Update, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums, reinsurance and other receivables		(97)
Asset		280
Deferred policy acquisition costs and value of business acquired		(3,330)
Deferred income tax asset		(391)
Other assets		(1)
Total Assets		(3,539)
Future policy benefits		(17,006)
Policyholder account balance		7,515
Liability		3,763
Other Policy-Related Balances		(1,227)
Deferred income tax liability		625
Other liabilities		(47)
Total Liabilities		(6,377)
Retained earnings		(1,621)
Accumulated other comprehensive income (loss)		4,462
Total MetLife, Inc.’s stockholders’ equity		2,841
Noncontrolling interests		(3)
Total equity		2,838
Total liabilities and equity		$ (3,539)