Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 18,072	$ 13,052
OCI before reclassifications	(10,170)	(606)
Deferred income tax benefit (expense)	2,222	91
AOCI before reclassifications, net of income tax	10,124	12,537
Amounts reclassified from AOCI	218	272
Deferred income tax benefit (expense)	(46)	(52)
Amounts reclassified from AOCI, net of income tax	172	220
Balance, end of period	10,397	12,757
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	22,217	18,283
OCI before reclassifications	(7,978)	(3,619)
Deferred income tax benefit (expense)	1,946	927
AOCI before reclassifications, net of income tax	16,185	15,591
Amounts reclassified from AOCI	30	(187)
Deferred income tax benefit (expense)	(7)	48
Amounts reclassified from AOCI, net of income tax	23	(139)
Balance, end of period	16,194	15,452
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	1,513	1,698
OCI before reclassifications	(1,442)	3,687
Deferred income tax benefit (expense)	310	(810)
AOCI before reclassifications, net of income tax	381	4,575
Amounts reclassified from AOCI	174	438
Deferred income tax benefit (expense)	(37)	(96)
Amounts reclassified from AOCI, net of income tax	137	342
Balance, end of period	518	4,917
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(3,795)	(4,927)
OCI before reclassifications	(753)	(674)
Deferred income tax benefit (expense)	(34)	(26)
AOCI before reclassifications, net of income tax	(4,582)	(5,627)
Amounts reclassified from AOCI	0	0
Deferred income tax benefit (expense)	0	0
Amounts reclassified from AOCI, net of income tax	0	0
Balance, end of period	(4,467)	(5,627)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(1,863)	(2,002)
OCI before reclassifications	3	0
Deferred income tax benefit (expense)	0	0
AOCI before reclassifications, net of income tax	(1,860)	(2,002)
Amounts reclassified from AOCI	14	21
Deferred income tax benefit (expense)	(2)	(4)
Amounts reclassified from AOCI, net of income tax	12	17
Balance, end of period	(1,848)	$ (1,985)
Joint-stock Company MetLife Insurance Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	101
Joint-stock Company MetLife Insurance Company | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	(14)
Joint-stock Company MetLife Insurance Company | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0
Joint-stock Company MetLife Insurance Company | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	115
Joint-stock Company MetLife Insurance Company | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	$ 0