Business, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)			1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended
	Feb. 21, 2020 shares	Mar. 07, 2019 shares	Dec. 31, 2018 shares	Dec. 31, 2021 USD ($) banking_center	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 segment	Dec. 31, 2021 USD ($) banking_center subsidiary shares	Dec. 31, 2020 USD ($)	Jan. 01, 2021 USD ($)	Dec. 28, 2018
Class of Stock [Line Items]
Number of subsidiaries | subsidiary									3
Number of banking centers | banking_center				24					24
Gain (loss) on sales					$ 3,800,000
Salary and compensation benefits, PPP loans										$ 7,800,000
Other operational expenses, PPP loans										700,000
Main Street Lending Program, fees received						$ 500,000
Main Street Lending Program, loans originated						$ 56,300,000	$ 56,300,000			$ 56,300,000
Financing receivable modification, CARES Act, percent				0.70%		0.70%	0.70%		0.70%	0.70%
Reportable business segments | segment								1,000
Cash reserve balances				$ 0		$ 0	$ 0		$ 0	$ 0
Securities receivable				1,500,000		1,900,000	1,900,000		1,500,000	1,900,000
Securities payable				25,200,000		0	0		25,200,000	0
Unamortized net deferred loan fees and origination costs				16,900,000		15,500,000	15,500,000		16,900,000	15,500,000
Mortgage servicing rights				$ 600,000		0	0		600,000	0
Goodwill impairment charge									$ 0	0
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]				Accrued interest receivable and other assets					Accrued interest receivable and other assets
Right-of-use asset				$ 141,139,000		0	0		$ 141,139,000	0	$ 54,500,000
Total lease obligations				142,956,000					142,956,000		$ 55,000,000
Operating lease liability noncurrent				136,595,000		0	0		136,595,000	0
Voluntary Early Retirement Plan
Class of Stock [Line Items]
Severance costs				3,500,000
Involuntary Early Retirement Plan
Class of Stock [Line Items]
Severance costs				1,800,000
COVID-19
Class of Stock [Line Items]
Financing receivable modification, CARES Act				1,100,000,000					1,100,000,000
COVID-19 | Deferral and/or Forbearance Period
Class of Stock [Line Items]
Financing receivable modification, CARES Act				$ 37,100,000		$ 43,400,000	43,400,000		37,100,000	$ 43,400,000
Paycheck Protection Program, CARES Act
Class of Stock [Line Items]
Notes receivable gross, PPP							$ 198,500,000		$ 2,700,000
Percent of total loans							3.40%		0.05%
Loans and leases receivable, sold					$ 95,100,000
Class B common stock
Class of Stock [Line Items]
Treasury stock, acquired (in shares) | shares									565,232
Class B common stock | Common Stock
Class of Stock [Line Items]
Treasury stock, acquired (in shares) | shares	932,459	2,112,321	1,400,000
Class B common stock | Mercantil Servicios Financieros, C.A. (MSF) | Maximum
Class of Stock [Line Items]
Percent of shares outstanding owned												5.00%
Florida
Class of Stock [Line Items]
Number of banking centers | banking_center				17					17
Right-of-use asset				$ 91,600,000					$ 91,600,000
Total lease obligations				$ 91,600,000					$ 91,600,000
Texas
Class of Stock [Line Items]
Number of banking centers | banking_center				7					7
Amerant Bank, N.A
Class of Stock [Line Items]
Ownership percentage of subsidiary				100.00%					100.00%
Amerant Mortgage
Class of Stock [Line Items]
Ownership percentage of subsidiary				51.00%					51.00%
Ownership percentage				49.00%					49.00%