Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Premiums									$ 42,235	$ 43,840	$ 38,992
Universal life and investment-type product policy fees									5,603	5,502	5,510
Net investment income									18,868	16,166	17,363
Other revenues									1,842	1,880	1,341
Net investment gains (losses)									444	(298)	(308)
Net derivative gains (losses)									628	851	(590)
Total revenues	$ 17,143	$ 18,678	$ 17,497	$ 16,302	$ 15,662	$ 16,289	$ 21,185	$ 14,805	69,620	67,941	62,308
Expenses
Policyholder benefits and claims and policyholder dividends									42,672	43,907	39,544
Interest credited to policyholder account balances									6,464	4,013	5,607
Capitalization of DAC									(3,358)	(3,254)	(3,002)
Amortization of DAC and VOBA									2,896	2,975	2,681
Amortization of negative VOBA									(33)	(56)	(140)
Interest expense on debt									955	1,122	1,129
Other expenses									13,229	12,927	12,953
Total expenses	$ 17,180	$ 15,887	$ 15,200	$ 14,558	$ 13,191	$ 15,210	$ 20,084	$ 13,149	62,825	61,634	58,772
Provision for income tax expense (benefit)									886	1,179	(1,470)
Income (loss) from continuing operations, net of income tax									5,909	5,128	5,006
U.S.
Expenses
Amortization of DAC and VOBA									475	477	459
Asia
Expenses
Amortization of DAC and VOBA									1,380	1,297	1,310
Latin America
Expenses
Amortization of DAC and VOBA									291	209	224
EMEA
Expenses
Amortization of DAC and VOBA									420	433	356
MetLife Holdings
Expenses
Amortization of DAC and VOBA									324	553	234
Corporate & Other
Expenses
Amortization of DAC and VOBA									6	6	98
Operating Segments
Revenues
Premiums									42,164	43,840	39,339
Universal life and investment-type product policy fees									5,395	5,382	5,407
Net investment income									17,830	17,383	16,544
Other revenues									1,585	1,556	1,454
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									66,974	68,161	62,744
Expenses
Policyholder benefits and claims and policyholder dividends									42,192	43,733	39,340
Interest credited to policyholder account balances									5,029	4,693	4,313
Capitalization of DAC									(3,338)	(3,253)	(3,036)
Amortization of DAC and VOBA									2,787	2,760	2,648
Amortization of negative VOBA									(33)	(55)	(131)
Interest expense on debt									955	1,059	1,145
Other expenses									12,778	12,529	12,409
Total expenses									60,370	61,466	56,688
Provision for income tax expense (benefit)									659	1,093	1,718
Adjusted earnings									5,945	5,602	4,338
Operating Segments | U.S.
Revenues
Premiums									26,801	28,186	23,632
Universal life and investment-type product policy fees									1,078	1,053	1,012
Net investment income									7,021	6,977	6,396
Other revenues									887	821	806
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									35,787	37,037	31,846
Expenses
Policyholder benefits and claims and policyholder dividends									26,165	27,765	23,627
Interest credited to policyholder account balances									1,984	1,790	1,474
Capitalization of DAC									(484)	(449)	(458)
Amortization of DAC and VOBA									475	477	459
Amortization of negative VOBA									0	0	0
Interest expense on debt									10	12	11
Other expenses									4,075	3,902	3,682
Total expenses									32,225	33,497	28,795
Provision for income tax expense (benefit)									724	736	1,024
Adjusted earnings									2,838	2,804	2,027
Operating Segments | Asia
Revenues
Premiums									6,632	6,766	6,755
Universal life and investment-type product policy fees									1,674	1,630	1,584
Net investment income									3,691	3,317	2,985
Other revenues									56	51	43
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									12,053	11,764	11,367
Expenses
Policyholder benefits and claims and policyholder dividends									5,185	5,326	5,075
Interest credited to policyholder account balances									1,710	1,465	1,351
Capitalization of DAC									(1,913)	(1,915)	(1,710)
Amortization of DAC and VOBA									1,288	1,302	1,300
Amortization of negative VOBA									(25)	(39)	(111)
Interest expense on debt									0	0	0
Other expenses									3,818	3,840	3,613
Total expenses									10,063	9,979	9,518
Provision for income tax expense (benefit)									585	548	620
Adjusted earnings									1,405	1,237	1,229
Operating Segments | Latin America
Revenues
Premiums									2,723	2,760	2,693
Universal life and investment-type product policy fees									1,094	1,050	1,044
Net investment income									1,271	1,239	1,219
Other revenues									44	35	32
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									5,132	5,084	4,988
Expenses
Policyholder benefits and claims and policyholder dividends									2,623	2,602	2,535
Interest credited to policyholder account balances									332	394	369
Capitalization of DAC									(396)	(377)	(364)
Amortization of DAC and VOBA									291	209	224
Amortization of negative VOBA									0	(1)	(1)
Interest expense on debt									3	6	5
Other expenses									1,443	1,421	1,479
Total expenses									4,296	4,254	4,247
Provision for income tax expense (benefit)									227	238	156
Adjusted earnings									609	592	585
Operating Segments | EMEA
Revenues
Premiums									2,177	2,131	2,061
Universal life and investment-type product policy fees									423	431	405
Net investment income									291	293	309
Other revenues									54	66	58
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									2,945	2,921	2,833
Expenses
Policyholder benefits and claims and policyholder dividends									1,176	1,127	1,077
Interest credited to policyholder account balances									98	100	100
Capitalization of DAC									(505)	(468)	(414)
Amortization of DAC and VOBA									428	434	357
Amortization of negative VOBA									(8)	(15)	(19)
Interest expense on debt									0	0	0
Other expenses									1,399	1,378	1,376
Total expenses									2,588	2,556	2,477
Provision for income tax expense (benefit)									75	88	59
Adjusted earnings									282	277	297
Operating Segments | MetLife Holdings
Revenues
Premiums									3,748	3,879	4,144
Universal life and investment-type product policy fees									1,124	1,218	1,361
Net investment income									5,281	5,379	5,607
Other revenues									253	250	244
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									10,406	10,726	11,356
Expenses
Policyholder benefits and claims and policyholder dividends									6,970	6,833	7,000
Interest credited to policyholder account balances									905	944	1,018
Capitalization of DAC									(28)	(36)	(82)
Amortization of DAC and VOBA									299	332	302
Amortization of negative VOBA									0	0	0
Interest expense on debt									8	9	24
Other expenses									969	1,081	1,365
Total expenses									9,123	9,163	9,627
Provision for income tax expense (benefit)									249	308	547
Adjusted earnings									1,034	1,255	1,182
Operating Segments | Corporate & Other
Revenues
Premiums									83	118	54
Universal life and investment-type product policy fees									2	0	1
Net investment income									275	178	28
Other revenues									291	333	271
Net investment gains (losses)									0	0	0
Net derivative gains (losses)									0	0	0
Total revenues									651	629	354
Expenses
Policyholder benefits and claims and policyholder dividends									73	80	26
Interest credited to policyholder account balances									0	0	1
Capitalization of DAC									(12)	(8)	(8)
Amortization of DAC and VOBA									6	6	6
Amortization of negative VOBA									0	0	0
Interest expense on debt									934	1,032	1,105
Other expenses									1,074	907	894
Total expenses									2,075	2,017	2,024
Provision for income tax expense (benefit)									(1,201)	(825)	(688)
Adjusted earnings									(223)	(563)	(982)
Significant Reconciling Items
Revenues
Premiums									71	0	(347)
Universal life and investment-type product policy fees									208	120	103
Net investment income									1,038	(1,217)	819
Other revenues									257	324	(113)
Net investment gains (losses)									444	(298)	(308)
Net derivative gains (losses)									628	851	(590)
Total revenues									2,646	(220)	(436)
Expenses
Policyholder benefits and claims and policyholder dividends									480	174	204
Interest credited to policyholder account balances									1,435	(680)	1,294
Capitalization of DAC									(20)	(1)	34
Amortization of DAC and VOBA									109	215	33
Amortization of negative VOBA									0	(1)	(9)
Interest expense on debt									0	63	(16)
Other expenses									451	398	544
Total expenses									2,455	168	2,084
Provision for income tax expense (benefit)									$ 227	$ 86	$ (3,188)