Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative effect of adoption of accounting principle, net of tax	Class A	Total Stockholders' Equity Before Noncontrolling Interest	Total Stockholders' Equity Before Noncontrolling Interest Cumulative effect of adoption of accounting principle, net of tax	Total Stockholders' Equity Before Noncontrolling Interest Class A	Common Stock Class A	Additional Paid in Capital	Treasury Stock	Treasury Stock Class A	Retained Earnings	Retained Earnings Cumulative effect of adoption of accounting principle, net of tax	Accumulated Other Comprehensive Income (loss)	Noncontrolling interest
Beginning balance (in shares) at Dec. 31, 2021							35,883,320
Beginning balance at Dec. 31, 2021	$ 831,873	$ (13,872)		$ 834,483	$ (13,872)		$ 3,589	$ 262,510	$ 0		$ 553,167	$ (13,872)	$ 15,217	$ (2,610)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Class A common stock (in shares)							(1,643,480)
Repurchase of Class A common stock			$ (54,820)			$ (54,820)				$ (54,820)
Treasury stock retired	0			0			$ (165)	(54,655)	54,820
Restricted stock issued (in shares)							104,762
Restricted stock issued	0			0			$ 10	(10)
Restricted stock surrendered (in shares)							(15,174)
Restricted stock and restricted stock units surrendered	(996)			(996)			$ (2)	(994)
Restricted stock forfeited (in shares)							(1,000)
Restricted stock forfeited	0			0
Restricted stock units vested (in shares)							22,394
Restricted stock units vested	0			0			$ 2	(2)
Stock-based compensation expense	1,260			1,260				1,260
Net income attributable to Amerant Bancorp Inc.	15,379			15,379							15,379
Dividends paid	(3,154)			(3,154)							(3,154)
Net loss attributable to noncontrolling-interest shareholders	(1,076)			0										(1,076)
Other comprehensive income (loss)	(39,641)			(39,641)									(39,641)
Ending balance (in shares) at Mar. 31, 2022							34,350,822
Ending balance at Mar. 31, 2022	734,953			738,639			$ 3,434	208,109	0		551,520		(24,424)	(3,686)
Beginning balance (in shares) at Dec. 31, 2021							35,883,320
Beginning balance at Dec. 31, 2021	831,873	$ (13,872)		834,483	$ (13,872)		$ 3,589	262,510	0		553,167	$ (13,872)	15,217	(2,610)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Amerant Bancorp Inc.	41,337
Net loss attributable to noncontrolling-interest shareholders	(1,192)
Other comprehensive income (loss)	(101,425)
Ending balance (in shares) at Sep. 30, 2022							33,773,249
Ending balance at Sep. 30, 2022	678,619			680,554			$ 3,376	191,970	0		571,416		(86,208)	(1,935)
Beginning balance (in shares) at Mar. 31, 2022							34,350,822
Beginning balance at Mar. 31, 2022	734,953			738,639			$ 3,434	208,109	0		551,520		(24,424)	(3,686)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Class A common stock (in shares)							(611,525)
Repurchase of Class A common stock			$ (17,240)			(17,240)				(17,240)
Treasury stock retired	0			0			$ (61)	(17,179)	17,240
Restricted stock issued (in shares)							37,938
Restricted stock issued	0			0			$ 4	(4)
Restricted stock forfeited (in shares)							(28,586)
Restricted stock forfeited	0			0			$ (3)	3
Restricted stock units vested (in shares)							10,955
Restricted stock units vested	0			0			$ 1	(1)
Stock-based compensation expense	1,276			1,276				1,276
Net income attributable to Amerant Bancorp Inc.	8,424			8,424							8,424
Dividends paid	(3,049)			(3,049)							(3,049)
Transfer of subsidiary shares from noncontrolling interest	0			(1,867)				(1,867)						1,867
Net loss attributable to noncontrolling-interest shareholders	(72)			0										(72)
Other comprehensive income (loss)	(26,535)			(26,535)									(26,535)
Ending balance (in shares) at Jun. 30, 2022							33,759,604
Ending balance at Jun. 30, 2022	697,757			699,648			$ 3,375	190,337	0		556,895		(50,959)	(1,891)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock issued (in shares)							22,200
Restricted stock issued	0			0			$ 2	(2)
Restricted stock surrendered (in shares)							(618)
Restricted stock and restricted stock units surrendered	(17)			(17)				(17)
Restricted stock forfeited (in shares)							(7,937)
Restricted stock forfeited	0			0			$ (1)	1
Stock-based compensation expense	1,651			1,651				1,651
Net income attributable to Amerant Bancorp Inc.	17,534			17,534							17,534
Dividends paid	(3,013)			(3,013)							(3,013)
Net loss attributable to noncontrolling-interest shareholders	(44)			0										(44)
Other comprehensive income (loss)	(35,249)			(35,249)									(35,249)
Ending balance (in shares) at Sep. 30, 2022							33,773,249
Ending balance at Sep. 30, 2022	678,619			680,554			$ 3,376	191,970	0		571,416		(86,208)	(1,935)
Beginning balance (in shares) at Dec. 31, 2022			33,815,161				33,815,161
Beginning balance at Dec. 31, 2022	705,726			707,816			$ 3,382	194,694	0		590,375		(80,635)	(2,090)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Class A common stock (in shares)							(22,403)
Repurchase of Class A common stock			$ (566)			(566)				(566)
Treasury stock retired	0			0			$ (2)	(564)	566
Restricted stock issued (in shares)							10,440
Restricted stock issued	0			0			$ 1	(1)
Restricted stock, restricted stock units and performance stock units surrendered (in shares)							(44,896)
Restricted stock, restricted stock units and performance stock units surrendered	(1,170)			(1,170)			$ (4)	(1,166)
Restricted stock forfeited (in shares)							(1,394)
Restricted stock forfeited	0			0
Performance stock units vested (in shares)							10,621
Performance stock units vested	0			0			$ 1	(1)
Restricted stock units vested (in shares)							46,731
Restricted stock units vested	0			0			$ 5	(5)
Stock-based compensation expense	1,825			1,825				1,825
Net income attributable to Amerant Bancorp Inc.	20,186			20,186							20,186
Dividends paid	(3,017)			(3,017)							(3,017)
Net loss attributable to noncontrolling-interest shareholders	(244)			0										(244)
Other comprehensive income (loss)	6,316			6,316									6,316
Ending balance (in shares) at Mar. 31, 2023							33,814,260
Ending balance at Mar. 31, 2023	729,056			731,390			$ 3,383	194,782	0		607,544		(74,319)	(2,334)
Beginning balance (in shares) at Dec. 31, 2022			33,815,161				33,815,161
Beginning balance at Dec. 31, 2022	705,726			707,816			$ 3,382	194,694	0		590,375		(80,635)	(2,090)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Class A common stock (in shares)							(259,853)
Stock issued for employee stock purchase plan (in shares)							30,557
Net income attributable to Amerant Bancorp Inc.	49,613
Net loss attributable to noncontrolling-interest shareholders	(884)
Other comprehensive income (loss)	(24,999)
Ending balance (in shares) at Sep. 30, 2023			33,583,621				33,583,621
Ending balance at Sep. 30, 2023	719,787			722,761			$ 3,359	194,103	0		630,933		(105,634)	(2,974)
Beginning balance (in shares) at Mar. 31, 2023							33,814,260
Beginning balance at Mar. 31, 2023	729,056			731,390			$ 3,383	194,782	0		607,544		(74,319)	(2,334)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Class A common stock (in shares)							(95,262)
Repurchase of Class A common stock			$ (1,659)			(1,659)				(1,659)
Treasury stock retired	0			0			$ (10)	(1,649)	1,659
Restricted stock, restricted stock units and performance stock units surrendered (in shares)							(4,414)
Restricted stock, restricted stock units and performance stock units surrendered	(199)			(199)			$ (1)	(198)
Stock issued for employee stock purchase plan	686			686			$ 3	683
Restricted stock forfeited (in shares)							(26,432)
Restricted stock forfeited	0			0			$ (3)	3
Restricted stock units vested (in shares)							17,450
Restricted stock units vested	0			0			$ 2	(2)
Stock-based compensation expense	1,656			1,656				1,656
Net income attributable to Amerant Bancorp Inc.	7,308			7,308							7,308
Dividends paid	(3,023)			(3,023)							(3,023)
Net loss attributable to noncontrolling-interest shareholders	(262)			0										(262)
Other comprehensive income (loss)	(12,607)			(12,607)									(12,607)
Ending balance (in shares) at Jun. 30, 2023							33,736,159
Ending balance at Jun. 30, 2023	720,956			723,552			$ 3,374	195,275	0		611,829		(86,926)	(2,596)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Class A common stock (in shares)							(142,188)
Repurchase of Class A common stock			$ (2,708)			$ (2,708)				$ 2,708
Treasury stock retired	0			0			$ (14)	(2,694)	2,708
Restricted stock, restricted stock units and performance stock units surrendered (in shares)							(2,124)
Restricted stock, restricted stock units and performance stock units surrendered								(17)
Restricted stock and restricted stock units surrendered	(17)			(17)
Restricted stock forfeited (in shares)							(8,865)
Restricted stock forfeited	0			0			$ (1)	1
Restricted stock units vested (in shares)							639
Restricted stock units vested	0			0
Stock-based compensation expense	1,538			1,538				1,538
Net income attributable to Amerant Bancorp Inc.	22,119			22,119							22,119
Dividends paid	(3,015)			(3,015)							(3,015)
Net loss attributable to noncontrolling-interest shareholders	(378)			0										(378)
Other comprehensive income (loss)	(18,708)			(18,708)									(18,708)
Ending balance (in shares) at Sep. 30, 2023			33,583,621				33,583,621
Ending balance at Sep. 30, 2023	$ 719,787			$ 722,761			$ 3,359	$ 194,103	$ 0		$ 630,933		$ (105,634)	$ (2,974)