Equity (Statutory Equity & Income - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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 360%	in excess of 390%
Metropolitan Life Insurance Company
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 11,098	$ 10,384
Statutory Accounting Practices, Prescribed Practice, Amount	1,200	1,100
Statutory Accounting Practices, Statutory Net Income Amount	3,656	1,982	$ 3,444
MetLife Reinsurance Company of Vermont
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Prescribed Practice, Amount	2,800	2,700
MetLife's Domestic Captive Life Reinsurance Subsidiaries
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	1,700	1,700
Statutory Accounting Practices, Statutory Net Income Amount	$ (59)	$ 2,100	$ (344)
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	$ 4,100
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 11,100