Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Premiums	$ 9,132	$ 8,736	$ 19,459	$ 18,202
Universal life and investment-type product policy fees	1,422	1,299	2,813	2,730
Net investment income	5,280	4,087	10,594	7,148
Other revenues	664	456	1,295	895
Net investment gains (losses)	1,605	231	1,739	(57)
Net derivative gains (losses)	421	(710)	(1,814)	3,491
Total revenues	18,524	14,099	34,086	32,409
Expenses
Policyholder benefits and claims and policyholder dividends	9,641	8,957	20,411	18,271
Interest credited to policyholder account balances	1,515	1,962	2,866	2,042
Capitalization of DAC	(642)	(671)	(1,417)	(1,445)
Amortization of DAC and VOBA	537	560	1,127	1,348
Amortization of negative VOBA	(10)	(10)	(19)	(20)
Interest expense on debt	228	232	456	454
Other expenses	2,768	2,872	5,884	5,919
Total expenses	14,037	13,902	29,308	26,569
Provision for income tax expense (benefit)	1,075	47	1,003	1,289
Net income (loss)	3,412	150	3,775	4,551
Operating Segments [Member]
Revenues
Premiums	9,132	8,716	18,594	18,150
Universal life and investment-type product policy fees	1,386	1,268	2,752	2,653
Net investment income	5,117	3,444	10,411	7,765
Other revenues	604	417	1,189	814
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	16,239	13,845	32,946	29,382
Expenses
Policyholder benefits and claims and policyholder dividends	9,565	8,713	19,671	18,076
Interest credited to policyholder account balances	1,150	1,161	2,291	2,379
Capitalization of DAC	(642)	(669)	(1,328)	(1,440)
Amortization of DAC and VOBA	540	568	1,048	1,307
Amortization of negative VOBA	(10)	(10)	(19)	(20)
Interest expense on debt	228	232	455	454
Other expenses	2,700	2,817	5,554	5,798
Total expenses	13,531	12,812	27,672	26,554
Provision for income tax expense (benefit)	584	198	1,117	512
Adjusted earnings	2,124	835	4,157	2,316
Segment Reconciling Items [Member]
Revenues
Premiums	0	20	865	52
Universal life and investment-type product policy fees	36	31	61	77
Net investment income	163	643	183	(617)
Other revenues	60	39	106	81
Net investment gains (losses)	1,605	231	1,739	(57)
Net derivative gains (losses)	421	(710)	(1,814)	3,491
Total revenues	2,285	254	1,140	3,027
Expenses
Policyholder benefits and claims and policyholder dividends	76	244	740	195
Interest credited to policyholder account balances	365	801	575	(337)
Capitalization of DAC	0	(2)	(89)	(5)
Amortization of DAC and VOBA	(3)	(8)	79	41
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	0	0	1	0
Other expenses	68	55	330	121
Total expenses	506	1,090	1,636	15
Provision for income tax expense (benefit)	491	(151)	(114)	777
U.S. | Operating Segments [Member]
Revenues
Premiums	5,474	5,184	11,173	10,858
Universal life and investment-type product policy fees	282	268	579	543
Net investment income	1,998	1,425	4,008	3,191
Other revenues	380	240	776	480
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	8,134	7,117	16,536	15,072
Expenses
Policyholder benefits and claims and policyholder dividends	5,739	5,038	11,881	10,473
Interest credited to policyholder account balances	359	412	718	870
Capitalization of DAC	(13)	(122)	(31)	(234)
Amortization of DAC and VOBA	8	115	24	234
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	2	2	3	4
Other expenses	898	1,012	1,809	2,078
Total expenses	6,993	6,457	14,404	13,425
Provision for income tax expense (benefit)	239	137	446	344
Adjusted earnings	902	523	1,686	1,303
Asia | Operating Segments [Member]
Revenues
Premiums	1,582	1,584	3,267	3,220
Universal life and investment-type product policy fees	436	420	894	850
Net investment income	1,158	767	2,422	1,704
Other revenues	19	14	37	28
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	3,195	2,785	6,620	5,802
Expenses
Policyholder benefits and claims and policyholder dividends	1,233	1,255	2,530	2,576
Interest credited to policyholder account balances	496	447	985	892
Capitalization of DAC	(395)	(351)	(830)	(772)
Amortization of DAC and VOBA	296	284	610	599
Amortization of negative VOBA	(8)	(8)	(15)	(16)
Interest expense on debt	0	0	0	0
Other expenses	832	797	1,731	1,671
Total expenses	2,454	2,424	5,011	4,950
Provision for income tax expense (benefit)	221	105	466	246
Adjusted earnings	520	256	1,143	606
Latin America | Operating Segments [Member]
Revenues
Premiums	636	489	1,231	1,129
Universal life and investment-type product policy fees	287	238	557	508
Net investment income	308	260	607	478
Other revenues	11	10	21	21
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	1,242	997	2,416	2,136
Expenses
Policyholder benefits and claims and policyholder dividends	724	449	1,485	1,059
Interest credited to policyholder account balances	60	56	119	126
Capitalization of DAC	(100)	(74)	(195)	(174)
Amortization of DAC and VOBA	83	70	143	144
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	1	1	2	2
Other expenses	343	307	678	652
Total expenses	1,111	809	2,232	1,809
Provision for income tax expense (benefit)	34	56	47	100
Adjusted earnings	97	132	137	227
EMEA | Operating Segments [Member]
Revenues
Premiums	621	557	1,219	1,125
Universal life and investment-type product policy fees	107	92	174	208
Net investment income	62	63	125	132
Other revenues	16	11	29	24
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	806	723	1,547	1,489
Expenses
Policyholder benefits and claims and policyholder dividends	333	263	676	573
Interest credited to policyholder account balances	25	27	49	54
Capitalization of DAC	(122)	(115)	(249)	(245)
Amortization of DAC and VOBA	94	85	156	215
Amortization of negative VOBA	(2)	(2)	(4)	(4)
Interest expense on debt	0	0	0	0
Other expenses	349	328	698	660
Total expenses	677	586	1,326	1,253
Provision for income tax expense (benefit)	35	21	56	42
Adjusted earnings	94	116	165	194
MetLife Holdings | Operating Segments [Member]
Revenues
Premiums	839	889	1,666	1,793
Universal life and investment-type product policy fees	273	249	547	543
Net investment income	1,543	981	3,189	2,296
Other revenues	69	70	131	105
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	2,724	2,189	5,533	4,737
Expenses
Policyholder benefits and claims and policyholder dividends	1,549	1,705	3,072	3,366
Interest credited to policyholder account balances	210	219	420	437
Capitalization of DAC	(9)	(5)	(17)	(10)
Amortization of DAC and VOBA	56	11	110	111
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	2	1	3	3
Other expenses	244	239	497	467
Total expenses	2,052	2,170	4,085	4,374
Provision for income tax expense (benefit)	136	(1)	294	66
Adjusted earnings	536	20	1,154	297
Corporate & Other | Operating Segments [Member]
Revenues
Premiums	(20)	13	38	25
Universal life and investment-type product policy fees	1	1	1	1
Net investment income	48	(52)	60	(36)
Other revenues	109	72	195	156
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	138	34	294	146
Expenses
Policyholder benefits and claims and policyholder dividends	(13)	3	27	29
Interest credited to policyholder account balances	0	0	0	0
Capitalization of DAC	(3)	(2)	(6)	(5)
Amortization of DAC and VOBA	3	3	5	4
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	223	228	447	445
Other expenses	34	134	141	270
Total expenses	244	366	614	743
Provision for income tax expense (benefit)	(81)	(120)	(192)	(286)
Adjusted earnings	$ (25)	$ (212)	$ (128)	$ (311)