Business, Basis of Presentation and Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)	$ 26,453	$ 35,113		$ 26,527	$ 34,683
Accumulated Other Comprehensive Income (Loss), Net of Tax	5,634	6,396		7,427	$ 5,366
Equity securities	1,544			2,513
Fair Value Option And Trading Securities	16,444			16,745
Other revenues	474	$ 342
Derivative assets	7,924			8,551
Derivative liabilities	4,075			4,339
Accrued Investment Income Receivable	3,638			3,524
Premiums and Other Receivables, Net	19,368			18,423
Payables For Collateral Under Securities Loaned And Other Transactions	26,151			25,723
Other Liabilities	24,013			$ 23,982
Adjustments for New Accounting Pronouncement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)			$ (1,200)
Accumulated Other Comprehensive Income (Loss), Net of Tax			1,200
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)			328
Equity securities			1,700
Fair Value Option And Trading Securities			$ 16,000
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other revenues	322
LCH update impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivative assets	(369)
Derivative liabilities	(203)
Accrued Investment Income Receivable	(14)
Premiums and Other Receivables, Net	(184)
Payables For Collateral Under Securities Loaned And Other Transactions	(365)
Other Liabilities	1
U.S. | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid legal plans and administrative-only contracts	129
MetLife Holdings | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Distribution and Servicing Fees	58
Corporate & Other | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee-based investment management service revenue	$ 71