Equity (Statutory Equity & Income - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Principal U.S. Insurance Subsidiaries, Excluding American Life
Statutory Accounting Practices [Line Items]
Combined RBC ratio of the principal U.S. insurance subsidiaries	in excess of 350%	in excess of 360%
Metropolitan Life Insurance Company
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Prescribed Practice, Amount	$ 1,600	$ 1,200
Statutory Accounting Practices, Statutory Net Income Amount	3,392	3,859	$ 3,656
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	11,312	10,915
MetLife Reinsurance Company of Vermont
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Prescribed Practice, Amount	2,000	2,000
MetLife's Domestic Captive Life Reinsurance Subsidiaries
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Net Income Amount	(7)	(27)	$ (59)
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 691	$ 695
Japan
Statutory Accounting Practices [Line Items]
Adjusted capital	in excess of four times the 200% solvency margin ratio	in excess of four times the 200% solvency margin ratio
Other Foreign Operations, Excluding Japan
Statutory Accounting Practices [Line Items]
Statutory capital and surplus required	$ 3,900
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 9,600