Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 10,397	$ 12,757	$ 18,072	$ 13,052
OCI before reclassifications	2,934	8,109	(7,236)	7,503
Deferred income tax benefit (expense)	(742)	(1,758)	1,480	(1,667)
AOCI before reclassifications, net of income tax	12,589	19,108	12,316	18,888
Amounts reclassified from AOCI	(129)	(364)	89	(92)
Deferred income tax benefit (expense)	25	67	(21)	15
Amounts reclassified from AOCI, net of income tax	(104)	(297)	68	(77)
Balance, end of period	12,309	18,563	12,309	18,563
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	16,194	15,452	22,217	18,283
OCI before reclassifications	2,099	8,505	(5,879)	4,886
Deferred income tax benefit (expense)	(570)	(1,902)	1,376	(975)
AOCI before reclassifications, net of income tax	17,723	22,055	17,714	22,194
Amounts reclassified from AOCI	(15)	(46)	15	(233)
Deferred income tax benefit (expense)	3	(2)	(4)	46
Amounts reclassified from AOCI, net of income tax	(12)	(48)	11	(187)
Balance, end of period	17,535	21,759	17,535	21,759
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	518	4,917	1,513	1,698
OCI before reclassifications	828	(639)	(614)	3,048
Deferred income tax benefit (expense)	(169)	142	141	(668)
AOCI before reclassifications, net of income tax	1,177	4,420	1,040	4,078
Amounts reclassified from AOCI	(131)	(340)	43	98
Deferred income tax benefit (expense)	27	74	(10)	(22)
Amounts reclassified from AOCI, net of income tax	(104)	(266)	33	76
Balance, end of period	1,073	4,154	1,073	4,154
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(4,467)	(5,627)	(3,795)	(4,927)
OCI before reclassifications	6	243	(747)	(431)
Deferred income tax benefit (expense)	(2)	2	(36)	(24)
AOCI before reclassifications, net of income tax	(4,463)	(5,382)	(4,578)	(5,382)
Amounts reclassified from AOCI	0	0	0	0
Deferred income tax benefit (expense)	0	0	0	0
Amounts reclassified from AOCI, net of income tax	0	0	0	0
Balance, end of period	(4,463)	(5,382)	(4,463)	(5,382)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(1,848)	(1,985)	(1,863)	(2,002)
OCI before reclassifications	1	0	4	0
Deferred income tax benefit (expense)	(1)	0	(1)	0
AOCI before reclassifications, net of income tax	(1,848)	(1,985)	(1,860)	(2,002)
Amounts reclassified from AOCI	17	22	31	43
Deferred income tax benefit (expense)	(5)	(5)	(7)	(9)
Amounts reclassified from AOCI, net of income tax	12	17	24	34
Balance, end of period	(1,836)	(1,968)	(1,836)	(1,968)
MetLife Hong Kong
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		248		248
MetLife Hong Kong | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		248		248
MetLife Hong Kong | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		0		0
MetLife Hong Kong | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		0		0
MetLife Hong Kong | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		$ 0		$ 0
Disposal Group, Held-for-Sale or Disposed of by Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	(176)		(75)
Disposal Group, Held-for-Sale or Disposed of by Sale | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	(176)		(190)
Disposal Group, Held-for-Sale or Disposed of by Sale | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0		0
Disposal Group, Held-for-Sale or Disposed of by Sale | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0		115
Disposal Group, Held-for-Sale or Disposed of by Sale | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	$ 0		$ 0