Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 03, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-38534
Entity Registrant Name	Amerant Bancorp Inc.
Entity Incorporation, State or Country Code	FL
Entity Tax Identification Number	65-0032379
Entity Address, Address Line One	220 Alhambra Circle
Entity Address, City or Town	Coral Gables
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	33134
City Area Code	305
Local Phone Number	460-8728
Title of 12(b) Security	Class A Common Stock, par value $0.10 per share
Trading Symbol	AMTB
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 609
Entity Common Stock, Shares Outstanding		34,634,126
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement pursuant to Regulation 14A for the 2022 Annual Meeting of Shareholders, to be filed within 120 days of the registrant’s fiscal year end, are incorporated by reference into Part III hereof.
Entity Central Index Key	0001734342
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false