Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 5,634	$ 6,396	$ 7,427	$ 5,366
OCI before reclassifications	(3,921)	3,453	(7,536)	4,694
Deferred income tax benefit (expense)	752	(1,132)	1,649	(1,354)
AOCI before reclassifications, net of income tax	2,465	8,717	1,540	8,706
Amounts reclassified from AOCI	584	(435)	495	(424)
Deferred income tax benefit (expense)	(195)	154	(185)	154
Amounts reclassified from AOCI, net of income tax	389	(281)	310	(270)
Balance, end of period	2,854	8,436	2,854	8,436
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	10,864	11,336	12,757	10,785
OCI before reclassifications	(3,096)	3,290	(6,907)	3,993
Deferred income tax benefit (expense)	706	(1,132)	1,541	(1,405)
AOCI before reclassifications, net of income tax	8,474	13,494	7,391	13,373
Amounts reclassified from AOCI	83	(47)	128	149
Deferred income tax benefit (expense)	(19)	22	(29)	(53)
Amounts reclassified from AOCI, net of income tax	64	(25)	99	96
Balance, end of period	8,538	13,469	8,538	13,469
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	683	1,853	905	1,865
OCI before reclassifications	141	(7)	(211)	203
Deferred income tax benefit (expense)	41	3	99	(70)
AOCI before reclassifications, net of income tax	865	1,849	793	1,998
Amounts reclassified from AOCI	470	(429)	305	(658)
Deferred income tax benefit (expense)	(170)	149	(143)	229
Amounts reclassified from AOCI, net of income tax	300	(280)	162	(429)
Balance, end of period	1,165	1,569	1,165	1,569
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(3,707)	(4,842)	(4,390)	(5,312)
OCI before reclassifications	(969)	169	(417)	517
Deferred income tax benefit (expense)	6	(6)	9	116
AOCI before reclassifications, net of income tax	(4,670)	(4,679)	(4,798)	(4,679)
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	(4,670)	(4,679)	(4,670)	(4,679)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(2,206)	(1,951)	(1,845)	(1,972)
OCI before reclassifications	3	1	(1)	(19)
Deferred income tax benefit (expense)	(1)	3	0	5
AOCI before reclassifications, net of income tax	(2,204)	(1,947)	(1,846)	(1,986)
Amounts reclassified from AOCI	31	41	62	85
Deferred income tax benefit (expense)	(6)	(17)	(13)	(22)
Amounts reclassified from AOCI, net of income tax	25	24	49	63
Balance, end of period	$ (2,179)	$ (1,923)	(2,179)	$ (1,923)
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, net of income tax			92
MetLife Afore | 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 | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax			0
MetLife Afore | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax			92
MetLife Afore | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax			$ 0