Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 23, 2018	Jun. 30, 2017
Document And Entity Information (Abstract)
Entity Registrant Name	Metropolitan Bank Holding Corp.
Entity Central Index Key	0001476034
Trading Symbol	mcb
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding		8,194,925
Entity Public Float			$ 97.3
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY