Consolidated Supplementary Insurance Information (Income Statement Items) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	$ 47,637	$ 47,838	$ 49,342
Net Investment Income	17,117	18,868	16,166
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	46,675	47,925	46,669
Amortization of DAC and VOBA Charged to Other Expenses	3,160	2,896	2,975
Other Expenses (1)	11,080	12,004	11,990
U.S.
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	28,335	27,879	29,239
Net Investment Income	6,563	6,821	6,703
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	27,966	28,165	29,539
Amortization of DAC and VOBA Charged to Other Expenses	471	475	477
Other Expenses (1)	3,716	3,603	3,466
Asia
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	8,554	8,482	8,390
Net Investment Income	3,931	3,920	3,055
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	7,249	7,278	6,559
Amortization of DAC and VOBA Charged to Other Expenses	1,468	1,380	1,297
Other Expenses (1)	1,825	1,907	1,903
Latin America
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	3,257	3,817	3,817
Net Investment Income	991	1,262	1,194
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	2,857	3,210	3,057
Amortization of DAC and VOBA Charged to Other Expenses	276	291	209
Other Expenses (1)	971	1,039	1,044
EMEA
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	2,709	2,615	2,587
Net Investment Income	697	1,442	(195)
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	1,623	2,361	772
Amortization of DAC and VOBA Charged to Other Expenses	452	420	433
Other Expenses (1)	860	921	909
MetLife Holdings
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	4,757	4,960	5,191
Net Investment Income	4,900	5,140	5,222
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	6,983	6,842	6,662
Amortization of DAC and VOBA Charged to Other Expenses	485	324	553
Other Expenses (1)	1,976	2,246	2,286
Corporate & Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	25	85	118
Net Investment Income	35	283	187
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	(3)	69	80
Amortization of DAC and VOBA Charged to Other Expenses	8	6	6
Other Expenses (1)	$ 1,732	$ 2,288	$ 2,382