Equity (Statutory Equity & Income and Dividend Restrictions - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
American Life Insurance Company
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 6,548	$ 5,895
Statutory net income (loss)	3,077	341	$ 335
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	2,200	0
MetLife Reinsurance Company of Vermont
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Prescribed Practice, Amount	2,700	5,600
MetLife's Domestic Captive Life Reinsurance Subsidiaries
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,700	4,400
Statutory net income (loss)	$ 2,100	$ (344)	(336)
Principal U.S. Insurance Subsidiaries, Excluding American Life
Statutory Accounting Practices [Line Items]
Combined RBC ratio of the principal U.S. insurance subsidiaries, including Brighthouse		in excess of 400%
Combined RBC ratio of the principal U.S. insurance subsidiaries, excluding Brighthouse	in excess of 390%	in excess of 400%
MetLife Reinsurance Company of Delaware
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Prescribed Practice, Amount		$ 260
Metropolitan Life Insurance Company
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 10,384	11,195
Statutory Accounting Practices, Prescribed Practice, Amount	1,100	909
Statutory net income (loss)	1,982	3,444	$ 3,703
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	2,523	$ 3,600
Other Foreign Operations, Excluding Japan
Statutory Accounting Practices [Line Items]
Statutory capital and surplus required	3,700
Statutory capital and surplus	$ 10,500
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