Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues
Premiums	$ 9,455	$ 9,935	$ 28,914	$ 28,137
Universal life and investment-type product policy fees	1,521	1,497	4,334	4,227
Net investment income	5,568	4,729	16,162	11,877
Other revenues	663	455	1,958	1,350
Net investment gains (losses)	(84)	(20)	1,655	(77)
Net derivative gains (losses)	(218)	(581)	(2,032)	2,910
Total revenues	16,905	16,015	50,991	48,424
Expenses
Policyholder benefits and claims and policyholder dividends	10,292	10,206	30,703	28,477
Interest credited to policyholder account balances	1,287	1,416	4,153	3,458
Capitalization of DAC	(635)	(764)	(2,052)	(2,209)
Amortization of DAC and VOBA	816	1,066	1,943	2,414
Amortization of negative VOBA	(6)	(15)	(25)	(35)
Interest expense on debt	240	229	696	683
Other expenses	2,869	2,954	8,753	8,873
Total expenses	14,863	15,092	44,171	41,661
Provision for income tax expense (benefit)	453	214	1,456	1,503
Net income (loss)	1,589	709	5,364	5,260
Operating Segments [Member]
Revenues
Premiums	9,398	9,935	27,992	28,085
Universal life and investment-type product policy fees	1,437	1,469	4,189	4,122
Net investment income	5,668	4,688	16,079	12,453
Other revenues	584	416	1,773	1,230
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	17,087	16,508	50,033	45,890
Expenses
Policyholder benefits and claims and policyholder dividends	10,111	9,969	29,782	28,045
Interest credited to policyholder account balances	1,167	1,149	3,458	3,528
Capitalization of DAC	(620)	(764)	(1,948)	(2,204)
Amortization of DAC and VOBA	758	995	1,806	2,302
Amortization of negative VOBA	(6)	(15)	(25)	(35)
Interest expense on debt	240	229	695	683
Other expenses	2,760	2,899	8,314	8,697
Total expenses	14,410	14,462	42,082	41,016
Provision for income tax expense (benefit)	552	409	1,669	921
Adjusted earnings	2,125	1,637	6,282	3,953
Segment Reconciling Items [Member]
Revenues
Premiums	57	0	922	52
Universal life and investment-type product policy fees	84	28	145	105
Net investment income	(100)	41	83	(576)
Other revenues	79	39	185	120
Net investment gains (losses)	(84)	(20)	1,655	(77)
Net derivative gains (losses)	(218)	(581)	(2,032)	2,910
Total revenues	(182)	(493)	958	2,534
Expenses
Policyholder benefits and claims and policyholder dividends	181	237	921	432
Interest credited to policyholder account balances	120	267	695	(70)
Capitalization of DAC	(15)	0	(104)	(5)
Amortization of DAC and VOBA	58	71	137	112
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	0	0	1	0
Other expenses	109	55	439	176
Total expenses	453	630	2,089	645
Provision for income tax expense (benefit)	(99)	(195)	(213)	582
U.S. | Operating Segments [Member]
Revenues
Premiums	5,746	6,333	16,919	17,191
Universal life and investment-type product policy fees	279	263	858	806
Net investment income	2,098	1,827	6,106	5,018
Other revenues	383	237	1,159	717
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	8,506	8,660	25,042	23,732
Expenses
Policyholder benefits and claims and policyholder dividends	6,118	6,108	17,999	16,581
Interest credited to policyholder account balances	362	381	1,080	1,251
Capitalization of DAC	(17)	(119)	(48)	(353)
Amortization of DAC and VOBA	26	123	50	357
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	1	2	4	6
Other expenses	886	1,026	2,695	3,104
Total expenses	7,376	7,521	21,780	20,946
Provision for income tax expense (benefit)	235	239	681	583
Adjusted earnings	895	900	2,581	2,203
Asia | Operating Segments [Member]
Revenues
Premiums	1,594	1,654	4,861	4,874
Universal life and investment-type product policy fees	477	595	1,371	1,445
Net investment income	1,354	1,088	3,776	2,792
Other revenues	17	16	54	44
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	3,442	3,353	10,062	9,155
Expenses
Policyholder benefits and claims and policyholder dividends	1,220	1,291	3,750	3,867
Interest credited to policyholder account balances	513	470	1,498	1,362
Capitalization of DAC	(373)	(431)	(1,203)	(1,203)
Amortization of DAC and VOBA	470	506	1,080	1,105
Amortization of negative VOBA	(5)	(14)	(20)	(30)
Interest expense on debt	0	0	0	0
Other expenses	811	869	2,542	2,540
Total expenses	2,636	2,691	7,647	7,641
Provision for income tax expense (benefit)	237	197	703	443
Adjusted earnings	569	465	1,712	1,071
Latin America | Operating Segments [Member]
Revenues
Premiums	705	529	1,936	1,658
Universal life and investment-type product policy fees	274	225	831	733
Net investment income	306	221	913	699
Other revenues	9	7	30	28
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	1,294	982	3,710	3,118
Expenses
Policyholder benefits and claims and policyholder dividends	885	575	2,370	1,634
Interest credited to policyholder account balances	63	52	182	178
Capitalization of DAC	(109)	(84)	(304)	(258)
Amortization of DAC and VOBA	62	62	205	206
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	2	1	4	3
Other expenses	363	313	1,041	965
Total expenses	1,266	919	3,498	2,728
Provision for income tax expense (benefit)	(1)	24	46	124
Adjusted earnings	29	39	166	266
EMEA | Operating Segments [Member]
Revenues
Premiums	532	551	1,751	1,676
Universal life and investment-type product policy fees	128	116	302	324
Net investment income	46	67	171	199
Other revenues	10	13	39	37
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	716	747	2,263	2,236
Expenses
Policyholder benefits and claims and policyholder dividends	268	304	944	877
Interest credited to policyholder account balances	17	29	66	83
Capitalization of DAC	(110)	(122)	(359)	(367)
Amortization of DAC and VOBA	118	125	274	340
Amortization of negative VOBA	(1)	(1)	(5)	(5)
Interest expense on debt	0	0	0	0
Other expenses	308	340	1,006	1,000
Total expenses	600	675	1,926	1,928
Provision for income tax expense (benefit)	22	20	78	62
Adjusted earnings	94	52	259	246
MetLife Holdings | Operating Segments [Member]
Revenues
Premiums	805	876	2,471	2,669
Universal life and investment-type product policy fees	279	269	826	812
Net investment income	1,771	1,427	4,960	3,723
Other revenues	57	61	188	166
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	2,912	2,633	8,445	7,370
Expenses
Policyholder benefits and claims and policyholder dividends	1,611	1,697	4,683	5,063
Interest credited to policyholder account balances	212	217	632	654
Capitalization of DAC	(8)	(5)	(25)	(15)
Amortization of DAC and VOBA	80	177	190	288
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	1	2	4	5
Other expenses	255	231	752	698
Total expenses	2,151	2,319	6,236	6,693
Provision for income tax expense (benefit)	155	61	449	127
Adjusted earnings	606	253	1,760	550
Corporate & Other | Operating Segments [Member]
Revenues
Premiums	16	(8)	54	17
Universal life and investment-type product policy fees	0	1	1	2
Net investment income	93	58	153	22
Other revenues	108	82	303	238
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	217	133	511	279
Expenses
Policyholder benefits and claims and policyholder dividends	9	(6)	36	23
Interest credited to policyholder account balances	0	0	0	0
Capitalization of DAC	(3)	(3)	(9)	(8)
Amortization of DAC and VOBA	2	2	7	6
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	236	224	683	669
Other expenses	137	120	278	390
Total expenses	381	337	995	1,080
Provision for income tax expense (benefit)	(96)	(132)	(288)	(418)
Adjusted earnings	$ (68)	$ (72)	$ (196)	$ (383)