Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Premiums	$ 10,242	$ 10,876	$ 34,573	$ 29,421
Universal life and investment-type product policy fees	1,343	1,428	4,105	4,152
Net investment income	4,486	4,295	12,704	12,909
Other revenues	479	301	1,428	935
Net investment gains (losses)	117	(606)	(443)	(414)
Net derivative gains (losses)	(378)	(123)	(88)	(535)
Total revenues	16,289	16,171	52,279	46,468
Expenses
Policyholder benefits and claims and policyholder dividends	10,407	11,030	34,597	29,943
Interest credited to policyholder account balances	1,334	1,338	3,527	4,081
Capitalization of DAC	(810)	(761)	(2,440)	(2,218)
Amortization of DAC and VOBA	732	626	2,132	1,945
Amortization of negative VOBA	(7)	(32)	(45)	(113)
Interest expense on debt	267	284	862	851
Other expenses	3,287	3,201	9,810	9,404
Total expenses	15,210	15,686	48,443	43,893
Provision for income tax expense (benefit)	164	(398)	770	(116)
Income (loss) from continuing operations, net of income tax	915	883	3,066	2,691
Operating Segments
Revenues
Premiums	10,242	10,913	34,573	29,768
Universal life and investment-type product policy fees	1,300	1,392	4,004	4,078
Net investment income	4,462	4,156	13,008	12,441
Other revenues	396	315	1,179	1,054
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	16,400	16,776	52,764	47,341
Expenses
Policyholder benefits and claims and policyholder dividends	10,252	10,800	34,345	29,737
Interest credited to policyholder account balances	1,202	1,105	3,476	3,207
Capitalization of DAC	(810)	(765)	(2,439)	(2,252)
Amortization of DAC and VOBA	624	553	2,029	1,905
Amortization of negative VOBA	(7)	(30)	(44)	(105)
Interest expense on debt	252	284	817	867
Other expenses	3,187	3,121	9,474	9,132
Total expenses	14,700	15,068	47,658	42,491
Provision for income tax expense (benefit)	292	587	897	1,235
Adjusted earnings	1,408	1,121	4,209	3,615
Operating Segments | U.S.
Revenues
Premiums	6,431	6,987	22,950	18,049
Universal life and investment-type product policy fees	252	247	772	763
Net investment income	1,787	1,602	5,168	4,789
Other revenues	206	197	613	600
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	8,676	9,033	29,503	24,201
Expenses
Policyholder benefits and claims and policyholder dividends	6,219	6,916	22,590	18,047
Interest credited to policyholder account balances	457	376	1,303	1,086
Capitalization of DAC	(116)	(126)	(336)	(342)
Amortization of DAC and VOBA	128	118	357	346
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	2	2	8	8
Other expenses	982	933	2,908	2,756
Total expenses	7,672	8,219	26,830	21,901
Provision for income tax expense (benefit)	209	275	554	771
Adjusted earnings	795	539	2,119	1,529
Operating Segments | Asia
Revenues
Premiums	1,689	1,696	5,091	5,063
Universal life and investment-type product policy fees	428	458	1,221	1,199
Net investment income	830	762	2,464	2,193
Other revenues	12	11	40	32
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	2,959	2,927	8,816	8,487
Expenses
Policyholder benefits and claims and policyholder dividends	1,354	1,223	3,934	3,785
Interest credited to policyholder account balances	381	349	1,094	1,003
Capitalization of DAC	(478)	(420)	(1,438)	(1,268)
Amortization of DAC and VOBA	366	424	993	1,005
Amortization of negative VOBA	(4)	(24)	(31)	(91)
Interest expense on debt	0	0	0	0
Other expenses	943	905	2,871	2,675
Total expenses	2,562	2,457	7,423	7,109
Provision for income tax expense (benefit)	131	156	437	459
Adjusted earnings	266	314	956	919
Operating Segments | Latin America
Revenues
Premiums	692	701	2,079	1,993
Universal life and investment-type product policy fees	229	229	786	764
Net investment income	339	299	942	891
Other revenues	7	7	24	24
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	1,267	1,236	3,831	3,672
Expenses
Policyholder benefits and claims and policyholder dividends	670	640	1,976	1,869
Interest credited to policyholder account balances	102	99	295	275
Capitalization of DAC	(97)	(94)	(282)	(264)
Amortization of DAC and VOBA	5	0	136	146
Amortization of negative VOBA	(1)	(1)	(1)	(1)
Interest expense on debt	2	1	5	4
Other expenses	351	377	1,052	1,060
Total expenses	1,032	1,022	3,181	3,089
Provision for income tax expense (benefit)	65	51	195	123
Adjusted earnings	170	163	455	460
Operating Segments | EMEA
Revenues
Premiums	514	527	1,611	1,534
Universal life and investment-type product policy fees	105	109	324	296
Net investment income	73	77	221	229
Other revenues	15	(2)	51	43
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	707	711	2,207	2,102
Expenses
Policyholder benefits and claims and policyholder dividends	281	282	861	821
Interest credited to policyholder account balances	24	26	75	75
Capitalization of DAC	(109)	(109)	(348)	(301)
Amortization of DAC and VOBA	110	78	324	260
Amortization of negative VOBA	(2)	(5)	(12)	(13)
Interest expense on debt	0	0	0	0
Other expenses	333	347	1,023	995
Total expenses	637	619	1,923	1,837
Provision for income tax expense (benefit)	15	21	62	47
Adjusted earnings	55	71	222	218
Operating Segments | MetLife Holdings
Revenues
Premiums	949	989	2,856	3,070
Universal life and investment-type product policy fees	286	349	901	1,056
Net investment income	1,375	1,390	4,056	4,232
Other revenues	70	37	205	170
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	2,680	2,765	8,018	8,528
Expenses
Policyholder benefits and claims and policyholder dividends	1,766	1,732	5,022	5,182
Interest credited to policyholder account balances	238	255	709	767
Capitalization of DAC	(8)	(14)	(28)	(71)
Amortization of DAC and VOBA	13	(70)	214	143
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	2	2	6	22
Other expenses	264	322	815	1,032
Total expenses	2,275	2,227	6,738	7,075
Provision for income tax expense (benefit)	78	174	248	465
Adjusted earnings	327	364	1,032	988
Operating Segments | Corporate & Other
Revenues
Premiums	(33)	13	(14)	59
Universal life and investment-type product policy fees	0	0	0	0
Net investment income	58	26	157	107
Other revenues	86	65	246	185
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	111	104	389	351
Expenses
Policyholder benefits and claims and policyholder dividends	(38)	7	(38)	33
Interest credited to policyholder account balances	0	0	0	1
Capitalization of DAC	(2)	(2)	(7)	(6)
Amortization of DAC and VOBA	2	3	5	5
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	246	279	798	833
Other expenses	314	237	805	614
Total expenses	522	524	1,563	1,480
Provision for income tax expense (benefit)	(206)	(90)	(599)	(630)
Adjusted earnings	(205)	(330)	(575)	(499)
Significant Reconciling Items
Revenues
Premiums	0	(37)	0	(347)
Universal life and investment-type product policy fees	43	36	101	74
Net investment income	24	139	(304)	468
Other revenues	83	(14)	249	(119)
Net investment gains (losses)	117	(606)	(443)	(414)
Net derivative gains (losses)	(378)	(123)	(88)	(535)
Total revenues	(111)	(605)	(485)	(873)
Expenses
Policyholder benefits and claims and policyholder dividends	155	230	252	206
Interest credited to policyholder account balances	132	233	51	874
Capitalization of DAC	0	4	(1)	34
Amortization of DAC and VOBA	108	73	103	40
Amortization of negative VOBA	0	(2)	(1)	(8)
Interest expense on debt	15	0	45	(16)
Other expenses	100	80	336	272
Total expenses	510	618	785	1,402
Provision for income tax expense (benefit)	$ (128)	$ (985)	$ (127)	$ (1,351)