Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Class A	Class B	Total Stockholders' Equity Before Noncontrolling Interest	Total Stockholders' Equity Before Noncontrolling Interest Cumulative Effect, Period of Adoption, Adjustment	Total Stockholders' Equity Before Noncontrolling Interest Class A	Total Stockholders' Equity Before Noncontrolling Interest Class B	Common Stock Class A	Common Stock Class B	Additional Paid in Capital	Treasury Stock	Treasury Stock Class A	Treasury Stock Class B	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2018									26,851,832	16,330,917
Beginning balance at Dec. 31, 2018	$ 747,418	$ 0			$ 747,418	$ 0			$ 2,686	$ 1,775	$ 385,367	$ (17,908)			$ 393,662	$ (872)	$ (18,164)	$ 872	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (in shares)									2,132,865
Common stock issued	29,218				29,218				$ 213		29,005
Repurchase of common stock (in shares)										(2,112,321)
Repurchase of common stock	(28,465)				(28,465)							(28,465)
Restricted stock issued (in shares)									3,882
Restricted stock issued	0				0
Issuance of common shares for restricted stock unit vesting (in shares)									16,025
Issuance of common shares for restricted stock unit vesting	0				0				$ 2		(2)
Restricted stock surrendered (in shares)									(77,028)
Restricted stock surrendered	(1,695)				(1,695)				$ (8)		(1,687)
Stock-based compensation expense	6,365				6,365						6,365
Net income attributable to Amerant Bancorp Inc.	51,334				51,334										51,334
Net loss attributable to noncontrolling-interest shareholders	0
Other comprehensive income	30,526				30,526												30,526
Other comprehensive income (loss)	31,398
Ending (in shares) at Dec. 31, 2019									28,927,576	14,218,596
Ending balance at Dec. 31, 2019	834,701				834,701				$ 2,893	$ 1,775	419,048	(46,373)			444,124		13,234		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock (in shares)										(5,182,244)
Repurchase of common stock	(69,378)				(69,378)							(69,378)
Treasury stock retired	0				0					$ (871)	(114,880)	115,751
Restricted stock issued (in shares)									6,591
Restricted stock issued	0				0				$ 1		(1)
Issuance of common shares for restricted stock unit vesting (in shares)									19,464
Issuance of common shares for restricted stock unit vesting	0				0				$ 2		(2)
Restricted stock surrendered (in shares)									(60,606)
Restricted stock surrendered	(917)				(917)				$ (6)		(911)
Restricted Stock forfeited (in shares)									(86,681)
Restricted Stock forfeited	0				0				$ (8)		8
Stock-based compensation expense	2,307				2,307						2,307
Net income attributable to Amerant Bancorp Inc.	(1,722)				(1,722)										(1,722)
Net loss attributable to noncontrolling-interest shareholders	0
Other comprehensive income (loss)	18,430				18,430												18,430
Ending (in shares) at Dec. 31, 2020			28,806,344	9,036,352					28,806,344	9,036,352
Ending balance at Dec. 31, 2020	783,421				783,421				$ 2,882	$ 904	305,569	0			442,402		31,664		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of stock (in shares)									8,047,564	(8,471,120)
Conversion of stock	0				0				$ 805	$ (847)	(42)
Repurchase of common stock (in shares)									(1,175,119)	(565,232)
Repurchase of common stock			$ (36,332)	$ (9,563)			$ (36,332)	$ (9,563)					$ (36,332)	$ (9,563)
Treasury stock retired	0				0				$ (118)	$ (57)	(45,720)	45,895
Restricted stock issued (in shares)									252,503
Restricted stock issued	0				0				$ 25		(25)
Issuance of common shares for restricted stock unit vesting (in shares)									45,586
Issuance of common shares for restricted stock unit vesting	0				0				$ 5		(5)
Issuance of common shares for performance shares unit vesting (in shares)									1,729
Issuance of common shares for performance shares unit vesting	0				0
Restricted stock surrendered (in shares)									(66,491)
Restricted stock surrendered	(2,143)				(2,143)				$ (7)		(2,136)
Restricted Stock forfeited (in shares)									(28,796)
Restricted Stock forfeited	0				0				$ (3)		3
Stock-based compensation expense	4,782				4,782						4,782
Dividends declared	(2,156)				(2,156)										(2,156)
Net income attributable to Amerant Bancorp Inc.	112,921				112,921										112,921
Net loss attributable to noncontrolling-interest shareholders	(2,610)				0														(2,610)
Other comprehensive income (loss)	(16,447)				(16,447)												(16,447)
Ending (in shares) at Dec. 31, 2021			35,883,320	0					35,883,320	0
Ending balance at Dec. 31, 2021	$ 831,873				$ 834,483				$ 3,589	$ 0	$ 262,510	$ 0			$ 553,167		$ 15,217		$ (2,610)