Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 7,427	$ 5,366
OCI before reclassifications	(3,615)	1,241
Deferred income tax benefit (expense)	897	(222)
AOCI before reclassifications, net of income tax	4,709	6,385
Amounts reclassified from AOCI	(89)	11
Deferred income tax benefit (expense)	10	0
Amounts reclassified from AOCI, net of income tax	(79)	11
Balance, end of period	5,634	6,396
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	12,757	10,785
OCI before reclassifications	(3,811)	703
Deferred income tax benefit (expense)	835	(273)
AOCI before reclassifications, net of income tax	9,781	11,215
Amounts reclassified from AOCI	45	196
Deferred income tax benefit (expense)	(10)	(75)
Amounts reclassified from AOCI, net of income tax	35	121
Balance, end of period	10,864	11,336
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	905	1,865
OCI before reclassifications	(352)	210
Deferred income tax benefit (expense)	58	(73)
AOCI before reclassifications, net of income tax	611	2,002
Amounts reclassified from AOCI	(165)	(229)
Deferred income tax benefit (expense)	27	80
Amounts reclassified from AOCI, net of income tax	(138)	(149)
Balance, end of period	683	1,853
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(4,390)	(5,312)
OCI before reclassifications	552	348
Deferred income tax benefit (expense)	3	122
AOCI before reclassifications, net of income tax	(3,835)	(4,842)
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	(3,707)	(4,842)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(1,845)	(1,972)
OCI before reclassifications	(4)	(20)
Deferred income tax benefit (expense)	1	2
AOCI before reclassifications, net of income tax	(1,848)	(1,990)
Amounts reclassified from AOCI	31	44
Deferred income tax benefit (expense)	(7)	(5)
Amounts reclassified from AOCI, net of income tax	24	39
Balance, end of period	(2,206)	$ (1,951)
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 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	92
MetLife Afore [Member] | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0
MetLife Afore [Member] | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0
MetLife Afore [Member] | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	92
MetLife Afore [Member] | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	$ 0