Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues
Premiums	$ 10,327	$ 9,466
Universal life and investment-type product policy fees	1,391	1,431
Net investment income	5,314	3,061
Other revenues	631	439
Net investment gains (losses)	134	(288)
Net derivative gains (losses)	(2,235)	4,201
Total revenues	15,562	18,310
Expenses
Policyholder benefits and claims and policyholder dividends	10,770	9,314
Interest credited to policyholder account balances	1,351	80
Capitalization of DAC	(775)	(774)
Amortization of DAC and VOBA	590	788
Amortization of negative VOBA	(9)	(10)
Interest expense on debt	228	222
Other expenses	3,116	3,047
Total expenses	15,271	12,667
Provision for income tax expense (benefit)	(72)	1,242
Net income (loss)	363	4,401
Operating Segments [Member]
Revenues
Premiums	9,462	9,434
Universal life and investment-type product policy fees	1,366	1,385
Net investment income	5,294	4,321
Other revenues	585	397
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	16,707	15,537
Expenses
Policyholder benefits and claims and policyholder dividends	10,106	9,363
Interest credited to policyholder account balances	1,141	1,218
Capitalization of DAC	(686)	(771)
Amortization of DAC and VOBA	508	739
Amortization of negative VOBA	(9)	(10)
Interest expense on debt	227	222
Other expenses	2,854	2,981
Total expenses	14,141	13,742
Provision for income tax expense (benefit)	533	314
Adjusted earnings	2,033	1,481
Segment Reconciling Items [Member]
Revenues
Premiums	865	32
Universal life and investment-type product policy fees	25	46
Net investment income	20	(1,260)
Other revenues	46	42
Net investment gains (losses)	134	(288)
Net derivative gains (losses)	(2,235)	4,201
Total revenues	(1,145)	2,773
Expenses
Policyholder benefits and claims and policyholder dividends	664	(49)
Interest credited to policyholder account balances	210	(1,138)
Capitalization of DAC	(89)	(3)
Amortization of DAC and VOBA	82	49
Amortization of negative VOBA	0	0
Interest expense on debt	1	0
Other expenses	262	66
Total expenses	1,130	(1,075)
Provision for income tax expense (benefit)	(605)	928
U.S. | Operating Segments [Member]
Revenues
Premiums	5,699	5,674
Universal life and investment-type product policy fees	297	275
Net investment income	2,010	1,766
Other revenues	396	240
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	8,402	7,955
Expenses
Policyholder benefits and claims and policyholder dividends	6,142	5,435
Interest credited to policyholder account balances	359	458
Capitalization of DAC	(18)	(112)
Amortization of DAC and VOBA	16	119
Amortization of negative VOBA	0	0
Interest expense on debt	1	2
Other expenses	911	1,066
Total expenses	7,411	6,968
Provision for income tax expense (benefit)	207	207
Adjusted earnings	784	780
Asia | Operating Segments [Member]
Revenues
Premiums	1,685	1,636
Universal life and investment-type product policy fees	458	430
Net investment income	1,264	937
Other revenues	18	14
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	3,425	3,017
Expenses
Policyholder benefits and claims and policyholder dividends	1,297	1,321
Interest credited to policyholder account balances	489	445
Capitalization of DAC	(435)	(421)
Amortization of DAC and VOBA	314	315
Amortization of negative VOBA	(7)	(8)
Interest expense on debt	0	0
Other expenses	899	874
Total expenses	2,557	2,526
Provision for income tax expense (benefit)	245	141
Adjusted earnings	623	350
Latin America | Operating Segments [Member]
Revenues
Premiums	595	640
Universal life and investment-type product policy fees	270	270
Net investment income	299	218
Other revenues	10	11
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	1,174	1,139
Expenses
Policyholder benefits and claims and policyholder dividends	761	610
Interest credited to policyholder account balances	59	70
Capitalization of DAC	(95)	(100)
Amortization of DAC and VOBA	60	74
Amortization of negative VOBA	0	0
Interest expense on debt	1	1
Other expenses	335	345
Total expenses	1,121	1,000
Provision for income tax expense (benefit)	13	44
Adjusted earnings	40	95
EMEA | Operating Segments [Member]
Revenues
Premiums	598	568
Universal life and investment-type product policy fees	67	116
Net investment income	63	69
Other revenues	13	13
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	741	766
Expenses
Policyholder benefits and claims and policyholder dividends	343	310
Interest credited to policyholder account balances	24	27
Capitalization of DAC	(127)	(130)
Amortization of DAC and VOBA	62	130
Amortization of negative VOBA	(2)	(2)
Interest expense on debt	0	0
Other expenses	349	332
Total expenses	649	667
Provision for income tax expense (benefit)	21	21
Adjusted earnings	71	78
MetLife Holdings | Operating Segments [Member]
Revenues
Premiums	827	904
Universal life and investment-type product policy fees	274	294
Net investment income	1,646	1,315
Other revenues	62	35
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	2,809	2,548
Expenses
Policyholder benefits and claims and policyholder dividends	1,523	1,661
Interest credited to policyholder account balances	210	218
Capitalization of DAC	(8)	(5)
Amortization of DAC and VOBA	54	100
Amortization of negative VOBA	0	0
Interest expense on debt	1	2
Other expenses	253	228
Total expenses	2,033	2,204
Provision for income tax expense (benefit)	158	67
Adjusted earnings	618	277
Corporate & Other | Operating Segments [Member]
Revenues
Premiums	58	12
Universal life and investment-type product policy fees	0	0
Net investment income	12	16
Other revenues	86	84
Net investment gains (losses)	0	0
Net derivative gains (losses)	0	0
Total revenues	156	112
Expenses
Policyholder benefits and claims and policyholder dividends	40	26
Interest credited to policyholder account balances	0	0
Capitalization of DAC	(3)	(3)
Amortization of DAC and VOBA	2	1
Amortization of negative VOBA	0	0
Interest expense on debt	224	217
Other expenses	107	136
Total expenses	370	377
Provision for income tax expense (benefit)	(111)	(166)
Adjusted earnings	$ (103)	$ (99)