Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Premiums									$ 38,992	$ 37,202	$ 36,403
Universal life and investment-type product policy fees									5,510	5,483	5,570
Net investment income									17,363	16,790	16,205
Other revenues									1,341	1,685	1,927
Net investment gains (losses)									(308)	317	609
Net derivative gains (losses)									(590)	(690)	629
Total revenues	$ 15,840	$ 16,171	$ 15,333	$ 14,964	$ 12,387	$ 15,806	$ 16,349	$ 16,245	62,308	60,787	61,343
Expenses
Policyholder benefits and claims and policyholder dividends									39,544	37,581	36,500
Interest credited to policyholder account balances									5,607	5,176	4,415
Capitalization of DAC									(3,002)	(3,152)	(3,319)
Amortization of DAC and VOBA									2,681	2,718	3,184
Amortization of negative VOBA									(140)	(269)	(361)
Interest expense on debt									1,129	1,157	1,168
Other expenses									12,953	13,295	14,105
Total expenses	14,879	15,686	14,315	13,892	14,058	14,717	13,979	13,752	58,772	56,506	55,692
Provision for income tax expense (benefit)									(1,470)	693	1,590
Income (loss) from continuing operations, net of income tax	$ 2,315	$ 883	$ 856	$ 952	$ (971)	$ 973	$ 1,686	$ 1,900	5,006	3,588	4,061
U.S.
Expenses
Amortization of DAC and VOBA									459	471	471
Asia
Expenses
Amortization of DAC and VOBA									1,310	1,350	1,262
Latin America
Expenses
Amortization of DAC and VOBA									224	184	271
EMEA
Expenses
Amortization of DAC and VOBA									356	408	492
MetLife Holdings
Expenses
Amortization of DAC and VOBA									234	424	722
Corporate & Other
Expenses
Amortization of DAC and VOBA									98	(119)	(34)
Operating Segments
Revenues
Premiums									39,339	37,505	36,868
Universal life and investment-type product policy fees									5,407	5,331	5,504
Net investment income									16,544	16,437	16,671
Other revenues									1,454	1,643	1,957
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									62,744	60,916	61,000
Expenses
Policyholder benefits and claims and policyholder dividends									39,340	37,876	36,793
Interest credited to policyholder account balances									4,313	4,088	4,079
Capitalization of DAC									(3,036)	(3,151)	(3,439)
Amortization of DAC and VOBA									2,648	3,043	3,068
Amortization of negative VOBA									(131)	(222)	(326)
Interest expense on debt									1,145	1,207	1,228
Other expenses									12,409	12,940	13,823
Total expenses									56,688	55,781	55,226
Provision for income tax expense (benefit)									1,718	999	1,744
Adjusted earnings									4,338	4,136	4,030
Operating Segments | U.S.
Revenues
Premiums									23,632	21,501	20,861
Universal life and investment-type product policy fees									1,012	989	943
Net investment income									6,396	6,206	6,183
Other revenues									806	784	751
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									31,846	29,480	28,738
Expenses
Policyholder benefits and claims and policyholder dividends									23,627	21,591	20,899
Interest credited to policyholder account balances									1,474	1,302	1,216
Capitalization of DAC									(458)	(471)	(493)
Amortization of DAC and VOBA									459	471	471
Amortization of negative VOBA									0	0	0
Interest expense on debt									11	9	4
Other expenses									3,682	3,706	3,685
Total expenses									28,795	26,608	25,782
Provision for income tax expense (benefit)									1,024	976	1,009
Adjusted earnings									2,027	1,896	1,947
Operating Segments | Asia
Revenues
Premiums									6,755	6,902	6,937
Universal life and investment-type product policy fees									1,584	1,488	1,542
Net investment income									2,985	2,707	2,675
Other revenues									43	61	105
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									11,367	11,158	11,259
Expenses
Policyholder benefits and claims and policyholder dividends									5,075	5,211	5,266
Interest credited to policyholder account balances									1,351	1,298	1,309
Capitalization of DAC									(1,710)	(1,668)	(1,720)
Amortization of DAC and VOBA									1,300	1,236	1,253
Amortization of negative VOBA									(111)	(208)	(309)
Interest expense on debt									0	0	0
Other expenses									3,613	3,586	3,611
Total expenses									9,518	9,455	9,410
Provision for income tax expense (benefit)									620	479	461
Adjusted earnings									1,229	1,224	1,388
Operating Segments | Latin America
Revenues
Premiums									2,693	2,529	2,581
Universal life and investment-type product policy fees									1,044	1,025	1,117
Net investment income									1,219	1,084	1,038
Other revenues									32	34	41
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									4,988	4,672	4,777
Expenses
Policyholder benefits and claims and policyholder dividends									2,535	2,443	2,408
Interest credited to policyholder account balances									369	328	349
Capitalization of DAC									(364)	(321)	(341)
Amortization of DAC and VOBA									224	184	271
Amortization of negative VOBA									(1)	(1)	(1)
Interest expense on debt									5	2	0
Other expenses									1,479	1,336	1,429
Total expenses									4,247	3,971	4,115
Provision for income tax expense (benefit)									156	158	37
Adjusted earnings									585	543	625
Operating Segments | EMEA
Revenues
Premiums									2,061	2,027	2,036
Universal life and investment-type product policy fees									405	391	424
Net investment income									309	318	326
Other revenues									58	73	61
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									2,833	2,809	2,847
Expenses
Policyholder benefits and claims and policyholder dividends									1,077	1,067	988
Interest credited to policyholder account balances									100	112	120
Capitalization of DAC									(414)	(403)	(472)
Amortization of DAC and VOBA									357	408	497
Amortization of negative VOBA									(19)	(13)	(16)
Interest expense on debt									0	0	0
Other expenses									1,376	1,323	1,469
Total expenses									2,477	2,494	2,586
Provision for income tax expense (benefit)									59	42	21
Adjusted earnings									297	273	240
Operating Segments | MetLife Holdings
Revenues
Premiums									4,144	4,506	4,545
Universal life and investment-type product policy fees									1,361	1,436	1,482
Net investment income									5,607	5,944	6,189
Other revenues									244	581	930
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									11,356	12,467	13,146
Expenses
Policyholder benefits and claims and policyholder dividends									7,000	7,523	7,346
Interest credited to policyholder account balances									1,018	1,042	1,062
Capitalization of DAC									(82)	(281)	(410)
Amortization of DAC and VOBA									302	736	577
Amortization of negative VOBA									0	0	0
Interest expense on debt									24	57	55
Other expenses									1,365	2,392	2,694
Total expenses									9,627	11,469	11,324
Provision for income tax expense (benefit)									547	292	582
Adjusted earnings									1,182	706	1,240
Operating Segments | Corporate & Other
Revenues
Premiums									54	40	(92)
Universal life and investment-type product policy fees									1	2	(4)
Net investment income									28	178	260
Other revenues									271	110	69
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									354	330	233
Expenses
Policyholder benefits and claims and policyholder dividends									26	41	(114)
Interest credited to policyholder account balances									1	6	23
Capitalization of DAC									(8)	(7)	(3)
Amortization of DAC and VOBA									6	8	(1)
Amortization of negative VOBA									0	0	0
Interest expense on debt									1,105	1,139	1,169
Other expenses									894	597	935
Total expenses									2,024	1,784	2,009
Provision for income tax expense (benefit)									(688)	(948)	(366)
Adjusted earnings									(982)	(506)	(1,410)
Significant Reconciling Items
Revenues
Premiums									(347)	(303)	(465)
Universal life and investment-type product policy fees									103	152	66
Net investment income									819	353	(466)
Other revenues									(113)	42	(30)
Net investment gains (losses)									(308)	317	609
Net derivative gains (losses)									(590)	(690)	629
Total revenues									(436)	(129)	343
Expenses
Policyholder benefits and claims and policyholder dividends									204	(295)	(293)
Interest credited to policyholder account balances									1,294	1,088	336
Capitalization of DAC									34	(1)	120
Amortization of DAC and VOBA									33	(325)	116
Amortization of negative VOBA									(9)	(47)	(35)
Interest expense on debt									(16)	(50)	(60)
Other expenses									544	355	282
Total expenses									2,084	725	466
Provision for income tax expense (benefit)									$ (3,188)	$ (306)	$ (154)