Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Premiums									$ 43,840	$ 38,992	$ 37,202
Universal life and investment-type product policy fees									5,502	5,510	5,483
Net investment income									16,166	17,363	16,790
Other revenues									1,880	1,341	1,685
Net investment gains (losses)									(298)	(308)	317
Net derivative gains (losses)									851	(590)	(690)
Total revenues	$ 15,662	$ 16,289	$ 21,185	$ 14,805	$ 15,840	$ 16,171	$ 15,333	$ 14,964	67,941	62,308	60,787
Expenses
Policyholder benefits and claims and policyholder dividends									43,907	39,544	37,581
Interest credited to policyholder account balances									4,013	5,607	5,176
Capitalization of DAC									(3,254)	(3,002)	(3,152)
Amortization of DAC and VOBA									2,975	2,681	2,718
Amortization of negative VOBA									(56)	(140)	(269)
Interest expense on debt									1,122	1,129	1,157
Other expenses									12,927	12,953	13,295
Total expenses	13,191	15,210	20,084	13,149	14,879	15,686	14,315	13,892	61,634	58,772	56,506
Provision for income tax expense (benefit)									1,179	(1,470)	693
Income (loss) from continuing operations, net of income tax	$ 2,062	$ 915	$ 894	$ 1,257	$ 2,315	$ 883	$ 856	$ 952	5,128	5,006	3,588
U.S.
Expenses
Amortization of DAC and VOBA									477	459	471
Asia
Expenses
Amortization of DAC and VOBA									1,297	1,310	1,350
Latin America
Expenses
Amortization of DAC and VOBA									209	224	184
EMEA
Expenses
Amortization of DAC and VOBA									433	356	408
MetLife Holdings
Expenses
Amortization of DAC and VOBA									553	234	424
Corporate & Other
Expenses
Amortization of DAC and VOBA									6	98	(119)
Operating Segments
Revenues
Premiums									43,840	39,339	37,505
Universal life and investment-type product policy fees									5,382	5,407	5,331
Net investment income									17,383	16,544	16,437
Other revenues									1,556	1,454	1,643
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									68,161	62,744	60,916
Expenses
Policyholder benefits and claims and policyholder dividends									43,733	39,340	37,876
Interest credited to policyholder account balances									4,693	4,313	4,088
Capitalization of DAC									(3,253)	(3,036)	(3,151)
Amortization of DAC and VOBA									2,760	2,648	3,043
Amortization of negative VOBA									(55)	(131)	(222)
Interest expense on debt									1,059	1,145	1,207
Other expenses									12,529	12,409	12,940
Total expenses									61,466	56,688	55,781
Provision for income tax expense (benefit)									1,093	1,718	999
Adjusted earnings									5,602	4,338	4,136
Operating Segments | U.S.
Revenues
Premiums									28,186	23,632	21,501
Universal life and investment-type product policy fees									1,053	1,012	989
Net investment income									6,977	6,396	6,206
Other revenues									821	806	784
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									37,037	31,846	29,480
Expenses
Policyholder benefits and claims and policyholder dividends									27,765	23,627	21,591
Interest credited to policyholder account balances									1,790	1,474	1,302
Capitalization of DAC									(449)	(458)	(471)
Amortization of DAC and VOBA									477	459	471
Amortization of negative VOBA									0	0	0
Interest expense on debt									12	11	9
Other expenses									3,902	3,682	3,706
Total expenses									33,497	28,795	26,608
Provision for income tax expense (benefit)									736	1,024	976
Adjusted earnings									2,804	2,027	1,896
Operating Segments | Asia
Revenues
Premiums									6,766	6,755	6,902
Universal life and investment-type product policy fees									1,630	1,584	1,488
Net investment income									3,317	2,985	2,707
Other revenues									51	43	61
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									11,764	11,367	11,158
Expenses
Policyholder benefits and claims and policyholder dividends									5,326	5,075	5,211
Interest credited to policyholder account balances									1,465	1,351	1,298
Capitalization of DAC									(1,915)	(1,710)	(1,668)
Amortization of DAC and VOBA									1,302	1,300	1,236
Amortization of negative VOBA									(39)	(111)	(208)
Interest expense on debt									0	0	0
Other expenses									3,840	3,613	3,586
Total expenses									9,979	9,518	9,455
Provision for income tax expense (benefit)									548	620	479
Adjusted earnings									1,237	1,229	1,224
Operating Segments | Latin America
Revenues
Premiums									2,760	2,693	2,529
Universal life and investment-type product policy fees									1,050	1,044	1,025
Net investment income									1,239	1,219	1,084
Other revenues									35	32	34
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									5,084	4,988	4,672
Expenses
Policyholder benefits and claims and policyholder dividends									2,602	2,535	2,443
Interest credited to policyholder account balances									394	369	328
Capitalization of DAC									(377)	(364)	(321)
Amortization of DAC and VOBA									209	224	184
Amortization of negative VOBA									(1)	(1)	(1)
Interest expense on debt									6	5	2
Other expenses									1,421	1,479	1,336
Total expenses									4,254	4,247	3,971
Provision for income tax expense (benefit)									238	156	158
Adjusted earnings									592	585	543
Operating Segments | EMEA
Revenues
Premiums									2,131	2,061	2,027
Universal life and investment-type product policy fees									431	405	391
Net investment income									293	309	318
Other revenues									66	58	73
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									2,921	2,833	2,809
Expenses
Policyholder benefits and claims and policyholder dividends									1,127	1,077	1,067
Interest credited to policyholder account balances									100	100	112
Capitalization of DAC									(468)	(414)	(403)
Amortization of DAC and VOBA									434	357	408
Amortization of negative VOBA									(15)	(19)	(13)
Interest expense on debt									0	0	0
Other expenses									1,378	1,376	1,323
Total expenses									2,556	2,477	2,494
Provision for income tax expense (benefit)									88	59	42
Adjusted earnings									277	297	273
Operating Segments | MetLife Holdings
Revenues
Premiums									3,879	4,144	4,506
Universal life and investment-type product policy fees									1,218	1,361	1,436
Net investment income									5,379	5,607	5,944
Other revenues									250	244	581
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									10,726	11,356	12,467
Expenses
Policyholder benefits and claims and policyholder dividends									6,833	7,000	7,523
Interest credited to policyholder account balances									944	1,018	1,042
Capitalization of DAC									(36)	(82)	(281)
Amortization of DAC and VOBA									332	302	736
Amortization of negative VOBA									0	0	0
Interest expense on debt									9	24	57
Other expenses									1,081	1,365	2,392
Total expenses									9,163	9,627	11,469
Provision for income tax expense (benefit)									308	547	292
Adjusted earnings									1,255	1,182	706
Operating Segments | Corporate & Other
Revenues
Premiums									118	54	40
Universal life and investment-type product policy fees									0	1	2
Net investment income									178	28	178
Other revenues									333	271	110
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									629	354	330
Expenses
Policyholder benefits and claims and policyholder dividends									80	26	41
Interest credited to policyholder account balances									0	1	6
Capitalization of DAC									(8)	(8)	(7)
Amortization of DAC and VOBA									6	6	8
Amortization of negative VOBA									0	0	0
Interest expense on debt									1,032	1,105	1,139
Other expenses									907	894	597
Total expenses									2,017	2,024	1,784
Provision for income tax expense (benefit)									(825)	(688)	(948)
Adjusted earnings									(563)	(982)	(506)
Significant Reconciling Items
Revenues
Premiums									0	(347)	(303)
Universal life and investment-type product policy fees									120	103	152
Net investment income									(1,217)	819	353
Other revenues									324	(113)	42
Net investment gains (losses)									(298)	(308)	317
Net derivative gains (losses)									851	(590)	(690)
Total revenues									(220)	(436)	(129)
Expenses
Policyholder benefits and claims and policyholder dividends									174	204	(295)
Interest credited to policyholder account balances									(680)	1,294	1,088
Capitalization of DAC									(1)	34	(1)
Amortization of DAC and VOBA									215	33	(325)
Amortization of negative VOBA									(1)	(9)	(47)
Interest expense on debt									63	(16)	(50)
Other expenses									398	544	355
Total expenses									168	2,084	725
Provision for income tax expense (benefit)									$ 86	$ (3,188)	$ (306)