Segment Information (Earnings) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Premiums	$ 15,153	$ 9,580	$ 24,331	$ 18,545
Universal life and investment-type product policy fees	1,370	1,364	2,762	2,724
Net investment income	4,473	4,193	8,218	8,614
Other revenues	475	292	949	634
Net investment gains (losses)	(227)	104	(560)	192
Net derivative gains (losses)	(59)	(200)	290	(412)
Total revenues	21,185	15,333	35,990	30,297
Expenses
Policyholder benefits and claims and policyholder dividends	15,175	9,740	24,190	18,913
Interest credited to policyholder account balances	1,424	1,292	2,193	2,743
Capitalization of DAC	(834)	(744)	(1,630)	(1,457)
Amortization of DAC and VOBA	707	656	1,400	1,319
Amortization of negative VOBA	(16)	(38)	(38)	(81)
Interest expense on debt	309	284	595	567
Other expenses	3,319	3,125	6,523	6,203
Total expenses	20,084	14,315	33,233	28,207
Provision for income tax expense (benefit)	207	162	606	282
Income (loss) from continuing operations, net of income tax	894	856	2,151	1,808
Operating Segments
Revenues
Premiums	15,153	9,716	24,331	18,855
Universal life and investment-type product policy fees	1,344	1,338	2,704	2,686
Net investment income	4,327	4,113	8,546	8,285
Other revenues	392	344	783	739
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	21,216	15,511	36,364	30,565
Expenses
Policyholder benefits and claims and policyholder dividends	15,125	9,718	24,093	18,937
Interest credited to policyholder account balances	1,157	1,066	2,274	2,102
Capitalization of DAC	(834)	(758)	(1,629)	(1,487)
Amortization of DAC and VOBA	708	707	1,405	1,352
Amortization of negative VOBA	(16)	(35)	(37)	(75)
Interest expense on debt	279	288	565	583
Other expenses	3,177	3,070	6,287	6,011
Total expenses	19,596	14,056	32,958	27,423
Provision for income tax expense (benefit)	248	288	605	648
Adjusted earnings	1,372	1,167	2,801	2,494
Operating Segments | U.S.
Revenues
Premiums	11,302	5,877	16,519	11,062
Universal life and investment-type product policy fees	262	251	520	516
Net investment income	1,719	1,575	3,381	3,187
Other revenues	203	199	407	403
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	13,486	7,902	20,827	15,168
Expenses
Policyholder benefits and claims and policyholder dividends	11,233	5,887	16,371	11,131
Interest credited to policyholder account balances	439	359	846	710
Capitalization of DAC	(114)	(116)	(220)	(216)
Amortization of DAC and VOBA	114	114	229	228
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	4	4	6	6
Other expenses	965	914	1,926	1,823
Total expenses	12,641	7,162	19,158	13,682
Provision for income tax expense (benefit)	174	247	345	496
Adjusted earnings	671	493	1,324	990
Operating Segments | Asia
Revenues
Premiums	1,654	1,659	3,402	3,367
Universal life and investment-type product policy fees	399	375	793	741
Net investment income	839	729	1,634	1,431
Other revenues	13	11	28	21
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	2,905	2,774	5,857	5,560
Expenses
Policyholder benefits and claims and policyholder dividends	1,237	1,247	2,580	2,562
Interest credited to policyholder account balances	362	333	713	654
Capitalization of DAC	(495)	(428)	(960)	(848)
Amortization of DAC and VOBA	313	290	627	581
Amortization of negative VOBA	(12)	(30)	(27)	(67)
Interest expense on debt	0	0	0	0
Other expenses	976	895	1,928	1,770
Total expenses	2,381	2,307	4,861	4,652
Provision for income tax expense (benefit)	161	157	306	303
Adjusted earnings	363	310	690	605
Operating Segments | Latin America
Revenues
Premiums	688	645	1,387	1,292
Universal life and investment-type product policy fees	275	275	557	535
Net investment income	327	289	603	592
Other revenues	9	8	17	17
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	1,299	1,217	2,564	2,436
Expenses
Policyholder benefits and claims and policyholder dividends	660	596	1,306	1,229
Interest credited to policyholder account balances	95	94	193	176
Capitalization of DAC	(91)	(88)	(185)	(170)
Amortization of DAC and VOBA	71	68	131	146
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	1	2	3	3
Other expenses	363	357	701	683
Total expenses	1,099	1,029	2,149	2,067
Provision for income tax expense (benefit)	55	34	130	72
Adjusted earnings	145	154	285	297
Operating Segments | EMEA
Revenues
Premiums	546	505	1,097	1,007
Universal life and investment-type product policy fees	107	92	219	187
Net investment income	73	78	148	152
Other revenues	20	28	36	45
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	746	703	1,500	1,391
Expenses
Policyholder benefits and claims and policyholder dividends	286	270	580	539
Interest credited to policyholder account balances	26	25	51	49
Capitalization of DAC	(121)	(100)	(239)	(192)
Amortization of DAC and VOBA	108	95	214	182
Amortization of negative VOBA	(4)	(5)	(10)	(8)
Interest expense on debt	0	0	0	0
Other expenses	339	332	690	648
Total expenses	634	617	1,286	1,218
Provision for income tax expense (benefit)	26	14	47	26
Adjusted earnings	86	72	167	147
Operating Segments | MetLife Holdings
Revenues
Premiums	957	1,022	1,907	2,081
Universal life and investment-type product policy fees	301	345	615	707
Net investment income	1,329	1,401	2,681	2,842
Other revenues	68	37	135	133
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	2,655	2,805	5,338	5,763
Expenses
Policyholder benefits and claims and policyholder dividends	1,706	1,717	3,256	3,450
Interest credited to policyholder account balances	235	255	471	512
Capitalization of DAC	(10)	(23)	(20)	(57)
Amortization of DAC and VOBA	101	139	201	213
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	2	5	4	20
Other expenses	275	370	551	710
Total expenses	2,309	2,463	4,463	4,848
Provision for income tax expense (benefit)	66	105	170	291
Adjusted earnings	280	237	705	624
Operating Segments | Corporate & Other
Revenues
Premiums	6	8	19	46
Universal life and investment-type product policy fees	0	0	0	0
Net investment income	40	41	99	81
Other revenues	79	61	160	120
Net investment gains (losses)	0	0	0	0
Net derivative gains (losses)	0	0	0	0
Total revenues	125	110	278	247
Expenses
Policyholder benefits and claims and policyholder dividends	3	1	0	26
Interest credited to policyholder account balances	0	0	0	1
Capitalization of DAC	(3)	(3)	(5)	(4)
Amortization of DAC and VOBA	1	1	3	2
Amortization of negative VOBA	0	0	0	0
Interest expense on debt	272	277	552	554
Other expenses	259	202	491	377
Total expenses	532	478	1,041	956
Provision for income tax expense (benefit)	(234)	(269)	(393)	(540)
Adjusted earnings	(173)	(99)	(370)	(169)
Significant Reconciling Items
Revenues
Premiums	0	(136)	0	(310)
Universal life and investment-type product policy fees	26	26	58	38
Net investment income	146	80	(328)	329
Other revenues	83	(52)	166	(105)
Net investment gains (losses)	(227)	104	(560)	192
Net derivative gains (losses)	(59)	(200)	290	(412)
Total revenues	(31)	(178)	(374)	(268)
Expenses
Policyholder benefits and claims and policyholder dividends	50	22	97	(24)
Interest credited to policyholder account balances	267	226	(81)	641
Capitalization of DAC	0	14	(1)	30
Amortization of DAC and VOBA	(1)	(51)	(5)	(33)
Amortization of negative VOBA	0	(3)	(1)	(6)
Interest expense on debt	30	(4)	30	(16)
Other expenses	142	55	236	192
Total expenses	488	259	275	784
Provision for income tax expense (benefit)	$ (41)	$ (126)	$ 1	$ (366)