Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 12,757	$ 6,911	$ 13,052	$ 1,722
OCI before reclassifications	8,109	6,307	7,503	12,982
Deferred income tax benefit (expense)	(1,758)	(1,435)	(1,667)	(2,951)
AOCI before reclassifications, net of income tax	19,108	11,783	18,888	11,753
Amounts reclassified from AOCI	(364)	(189)	(92)	(186)
Deferred income tax benefit (expense)	67	37	15	43
Amounts reclassified from AOCI, net of income tax	(297)	(152)	(77)	(143)
Balance, end of period	18,563	11,631	18,563	11,631
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	15,452	12,248	18,283	7,042
OCI before reclassifications	8,505	5,478	4,886	12,199
Deferred income tax benefit (expense)	(1,902)	(1,289)	(975)	(2,805)
AOCI before reclassifications, net of income tax	22,055	16,437	22,194	16,436
Amounts reclassified from AOCI	(46)	(127)	(233)	(129)
Deferred income tax benefit (expense)	(2)	30	46	30
Amounts reclassified from AOCI, net of income tax	(48)	(97)	(187)	(99)
Balance, end of period	21,759	16,340	21,759	16,340
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	4,917	1,614	1,698	1,613
OCI before reclassifications	(639)	658	3,048	647
Deferred income tax benefit (expense)	142	(153)	(668)	(147)
AOCI before reclassifications, net of income tax	4,420	2,119	4,078	2,113
Amounts reclassified from AOCI	(340)	(92)	98	(116)
Deferred income tax benefit (expense)	74	14	(22)	26
Amounts reclassified from AOCI, net of income tax	(266)	(78)	76	(90)
Balance, end of period	4,154	2,041	4,154	2,041
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(5,627)	(4,947)	(4,927)	(4,905)
OCI before reclassifications	243	174	(431)	138
Deferred income tax benefit (expense)	2	7	(24)	1
AOCI before reclassifications, net of income tax	(5,382)	(4,766)	(5,382)	(4,766)
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	(5,382)	(4,766)	(5,382)	(4,766)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(1,985)	(2,004)	(2,002)	(2,028)
OCI before reclassifications	0	(3)	0	(2)
Deferred income tax benefit (expense)	0	0	0	0
AOCI before reclassifications, net of income tax	(1,985)	(2,007)	(2,002)	(2,030)
Amounts reclassified from AOCI	22	30	43	59
Deferred income tax benefit (expense)	(5)	(7)	(9)	(13)
Amounts reclassified from AOCI, net of income tax	17	23	34	46
Balance, end of period	(1,968)	$ (1,984)	(1,968)	(1,984)
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
MetLife Hong Kong [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	(248)		(248)
MetLife Hong Kong [Member] | 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 [Member] | 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 [Member] | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0		0
MetLife Hong Kong [Member] | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	$ 0		$ 0