Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	$ 18,072	$ 13,052	$ 1,722
OCI before reclassifications	(9,272)	7,602	15,047
Deferred income tax benefit (expense)	1,837	(1,664)	(3,339)
AOCI before reclassifications, net of income tax	10,637	18,990	13,430
Amounts reclassified from AOCI	216	(1,287)	(415)
Deferred income tax benefit (expense)	(27)	421	16
Amounts reclassified from AOCI, net of income tax	189	(866)	(399)
Balance end of period	10,919	18,072	13,052
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	22,217	18,283	7,042
OCI before reclassifications	(7,829)	5,775	14,850
Deferred income tax benefit (expense)	1,918	(1,349)	(3,408)
AOCI before reclassifications, net of income tax	16,306	22,709	18,484
Amounts reclassified from AOCI	(125)	(357)	(265)
Deferred income tax benefit (expense)	29	83	61
Amounts reclassified from AOCI, net of income tax	(96)	(274)	(204)
Balance end of period	16,042	22,217	18,283
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	1,513	1,698	1,613
OCI before reclassifications	(113)	730	328
Deferred income tax benefit (expense)	18	(257)	34
AOCI before reclassifications, net of income tax	1,418	2,171	1,975
Amounts reclassified from AOCI	250	(1,016)	(268)
Deferred income tax benefit (expense)	(39)	358	(27)
Amounts reclassified from AOCI, net of income tax	211	(658)	(295)
Balance end of period	1,629	1,513	1,698
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	(3,795)	(4,927)	(4,905)
OCI before reclassifications	(1,567)	1,002	(43)
Deferred income tax benefit (expense)	(53)	(36)	21
AOCI before reclassifications, net of income tax	(5,415)	(3,961)	(4,927)
Amounts reclassified from AOCI	0	0	0
Deferred income tax benefit (expense)	0	0	0
Amounts reclassified from AOCI, net of income tax	0	0	0
Balance end of period	(5,154)	(3,795)	(4,927)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	(1,863)	(2,002)	(2,028)
OCI before reclassifications	237	95	(88)
Deferred income tax benefit (expense)	(46)	(22)	14
AOCI before reclassifications, net of income tax	(1,672)	(1,929)	(2,102)
Amounts reclassified from AOCI	91	86	118
Deferred income tax benefit (expense)	(17)	(20)	(18)
Amounts reclassified from AOCI, net of income tax	74	66	100
Balance end of period	(1,598)	(1,863)	(2,002)
MetLife Hong Kong
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		(52)
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		(218)
MetLife Hong Kong | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		0
MetLife Hong Kong | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		166
MetLife Hong Kong | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax		$ 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	93
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	(168)
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
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	261
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
Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			26
Deferred income tax benefit (expense)			(5)
Amounts reclassified from AOCI, net of income tax			21
Accounting Standards Update 2016-01 | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			4
Deferred income tax benefit (expense)			(1)
Amounts reclassified from AOCI, net of income tax			3
Accounting Standards Update 2016-01 | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			22
Deferred income tax benefit (expense)			(4)
Amounts reclassified from AOCI, net of income tax			18
Accounting Standards Update 2016-01 | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			0
Deferred income tax benefit (expense)			0
Amounts reclassified from AOCI, net of income tax			0
Accounting Standards Update 2016-01 | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			0
Deferred income tax benefit (expense)			0
Amounts reclassified from AOCI, net of income tax			$ 0