Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	$ 13,052	$ 1,722	$ 7,427
OCI before reclassifications	7,602	15,047	(9,114)
Deferred income tax benefit (expense)	(1,664)	(3,339)	1,921
AOCI before reclassifications, net of income tax	18,990	13,430	234
Amounts reclassified from AOCI	(1,287)	(415)	651
Deferred income tax benefit (expense)	421	16	(167)
Amounts reclassified from AOCI, net of income tax	(866)	(399)	484
Balance end of period	18,072	13,052	1,722
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	18,283	7,042	12,757
OCI before reclassifications	5,775	14,850	(8,735)
Deferred income tax benefit (expense)	(1,349)	(3,408)	1,961
AOCI before reclassifications, net of income tax	22,709	18,484	5,983
Amounts reclassified from AOCI	(357)	(265)	14
Deferred income tax benefit (expense)	83	61	(3)
Amounts reclassified from AOCI, net of income tax	(274)	(204)	11
Balance end of period	22,217	18,283	7,042
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	1,698	1,613	905
OCI before reclassifications	730	328	157
Deferred income tax benefit (expense)	(257)	34	(41)
AOCI before reclassifications, net of income tax	2,171	1,975	1,021
Amounts reclassified from AOCI	(1,016)	(268)	517
Deferred income tax benefit (expense)	358	(27)	(135)
Amounts reclassified from AOCI, net of income tax	(658)	(295)	382
Balance end of period	1,513	1,698	1,613
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	(4,927)	(4,905)	(4,390)
OCI before reclassifications	1,002	(43)	(679)
Deferred income tax benefit (expense)	(36)	21	36
AOCI before reclassifications, net of income tax	(3,961)	(4,927)	(5,033)
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	(3,795)	(4,927)	(4,905)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	(2,002)	(2,028)	(1,845)
OCI before reclassifications	95	(88)	143
Deferred income tax benefit (expense)	(22)	14	(35)
AOCI before reclassifications, net of income tax	(1,929)	(2,102)	(1,737)
Amounts reclassified from AOCI	86	118	120
Deferred income tax benefit (expense)	(20)	(18)	(29)
Amounts reclassified from AOCI, net of income tax	66	100	91
Balance end of period	(1,863)	(2,002)	(2,028)
MetLife Afore
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			92
MetLife Afore | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			0
MetLife Afore | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			0
MetLife Afore | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			92
MetLife Afore | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			0
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
Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			(425)
Deferred income tax benefit (expense)			1,337
Amounts reclassified from AOCI, net of income tax			912
Accounting Standards Update 2016-01 | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			(425)
Deferred income tax benefit (expense)			1,473
Amounts reclassified from AOCI, net of income tax			1,048
Accounting Standards Update 2016-01 | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI			0
Deferred income tax benefit (expense)			210
Amounts reclassified from AOCI, net of income tax			210
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)			36
Amounts reclassified from AOCI, net of income tax			36
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)			(382)
Amounts reclassified from AOCI, net of income tax			$ (382)
Accounting Standards Update 2017-12
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 2017-12 | 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 2017-12 | 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 2017-12 | 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 2017-12 | 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