Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 1,722	$ 7,427
OCI before reclassifications	6,675	(3,615)
Deferred income tax benefit (expense)	(1,516)	897
AOCI before reclassifications, net of income tax	6,881	4,709
Amounts reclassified from AOCI	3	(89)
Deferred income tax benefit (expense)	6	10
Amounts reclassified from AOCI, net of income tax	9	(79)
Balance, end of period	6,911	5,634
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	7,042	12,757
OCI before reclassifications	6,721	(3,811)
Deferred income tax benefit (expense)	(1,516)	835
AOCI before reclassifications, net of income tax	12,247	9,781
Amounts reclassified from AOCI	(2)	45
Deferred income tax benefit (expense)	0	(10)
Amounts reclassified from AOCI, net of income tax	(2)	35
Balance, end of period	12,248	10,864
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	1,613	905
OCI before reclassifications	(11)	(352)
Deferred income tax benefit (expense)	6	58
AOCI before reclassifications, net of income tax	1,608	611
Amounts reclassified from AOCI	(24)	(165)
Deferred income tax benefit (expense)	12	27
Amounts reclassified from AOCI, net of income tax	(12)	(138)
Balance, end of period	1,614	683
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(4,905)	(4,390)
OCI before reclassifications	(36)	552
Deferred income tax benefit (expense)	(6)	3
AOCI before reclassifications, net of income tax	(4,947)	(3,835)
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	(4,947)	(3,707)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(2,028)	(1,845)
OCI before reclassifications	1	(4)
Deferred income tax benefit (expense)	0	1
AOCI before reclassifications, net of income tax	(2,027)	(1,848)
Amounts reclassified from AOCI	29	31
Deferred income tax benefit (expense)	(6)	(7)
Amounts reclassified from AOCI, net of income tax	23	24
Balance, end of period	(2,004)	(2,206)
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
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)
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