Consolidated Supplementary Insurance Information (Income Statement Items) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	$ 44,502	$ 42,685	$ 41,973
Net Investment Income	17,363	16,790	16,205
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	43,920	41,534	39,559
Amortization of DAC and VOBA Charged to Other Expenses	2,681	2,718	3,184
Other Expenses (1)	12,171	12,254	12,949
U.S.
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	24,644	22,490	21,804
Net Investment Income	6,201	5,942	6,020
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	25,103	22,892	22,100
Amortization of DAC and VOBA Charged to Other Expenses	459	471	471
Other Expenses (1)	3,235	3,244	3,197
Asia
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	8,352	8,914	8,491
Net Investment Income	3,299	2,807	2,859
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	6,799	6,916	6,808
Amortization of DAC and VOBA Charged to Other Expenses	1,310	1,350	1,262
Other Expenses (1)	1,802	1,795	1,619
Latin America
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	3,737	3,554	3,702
Net Investment Income	1,288	1,133	1,046
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	2,973	2,770	2,853
Amortization of DAC and VOBA Charged to Other Expenses	224	184	271
Other Expenses (1)	1,111	1,007	1,075
EMEA
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	2,492	2,442	2,455
Net Investment Income	1,157	1,229	347
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	2,012	2,064	1,109
Amortization of DAC and VOBA Charged to Other Expenses	356	408	492
Other Expenses (1)	966	924	998
MetLife Holdings
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	5,603	6,034	6,116
Net Investment Income	5,426	5,670	5,855
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	7,097	7,521	7,215
Amortization of DAC and VOBA Charged to Other Expenses	234	424	722
Other Expenses (1)	2,550	3,392	3,597
Corporate & Other
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	(326)	(749)	(595)
Net Investment Income	(8)	9	78
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	(64)	(629)	(526)
Amortization of DAC and VOBA Charged to Other Expenses	98	(119)	(34)
Other Expenses (1)	$ 2,507	$ 1,892	$ 2,463