Consolidated Statements of Operations and Comprehensive Income - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest income
Loans	$ 216,097,000	$ 220,898,000	$ 263,011,000
Investment securities	31,500,000	39,023,000	47,210,000
Interest earning deposits with banks	247,000	633,000	2,753,000
Total interest income	247,844,000	260,554,000	312,974,000
Interest expense
Interest bearing demand deposits	591,000	439,000	925,000
Savings and money market deposits	3,533,000	7,128,000	15,690,000
Time deposits	23,766,000	45,765,000	51,757,000
Advances from the Federal Home Loan Bank	8,595,000	13,168,000	24,325,000
Senior notes	3,768,000	1,968,000	0
Junior subordinated debentures	2,449,000	2,533,000	7,184,000
Securities sold under agreements to repurchase	1,000	1,000	5,000
Total interest expense	42,703,000	71,002,000	99,886,000
Net interest income	205,141,000	189,552,000	213,088,000
Reversal of (provision for) loan losses	(16,500,000)	88,620,000	(3,150,000)
Net interest income after (reversal of) provision for loan losses	221,641,000	100,932,000	216,238,000
Noninterest income
Deposits and service fees	17,214,000	15,838,000	17,067,000
Brokerage, advisory and fiduciary activities	18,616,000	16,949,000	14,936,000
Change in cash surrender value of bank owned life insurance	5,459,000	5,695,000	5,710,000
Cards and trade finance servicing fees	1,771,000	1,346,000	3,925,000
Data processing and fees for other services	0	0	955,000
Securities gains, net	3,740,000	26,990,000	2,605,000
Loss on early extinguishment of advances from the Federal Home Loan Bank, net	(2,488,000)	(73,000)	(886,000)
Gain on sale of headquarters building	62,387,000	0	0
Loan-level derivative income	3,951,000	3,173,000	5,148,000
Other noninterest income	9,971,000	3,552,000	7,650,000
Total noninterest income	120,621,000	73,470,000	57,110,000
Noninterest expense
Salaries and employee benefits	117,585,000	111,469,000	137,380,000
Professional and other services fees	19,911,000	13,459,000	16,123,000
Occupancy and equipment	20,364,000	17,624,000	16,194,000
Telecommunication and data processing	14,949,000	12,931,000	13,063,000
Depreciation and amortization	7,269,000	9,385,000	7,094,000
FDIC assessments and insurance	6,423,000	6,141,000	4,043,000
Other operating expenses	11,741,000	7,727,000	15,420,000
Total noninterest expenses	198,242,000	178,736,000	209,317,000
Income (loss) before income tax (expense) benefit	144,020,000	(4,334,000)	64,031,000
Income tax (expense) benefit	(33,709,000)	2,612,000	(12,697,000)
Net income (loss) before attribution of noncontrolling interest	110,311,000	(1,722,000)	51,334,000
Net loss attributable to noncontrolling interest	(2,610,000)	0	0
Net income (loss) attributable to Amerant Bancorp Inc.	112,921,000	(1,722,000)	51,334,000
Other comprehensive (loss) income, net of tax
Net unrealized holding (losses) gains on securities available for sale arising during the period	(12,960,000)	39,941,000	32,810,000
Net unrealized holding gains (losses) on cash flow hedges arising during the period	137,000	(1,730,000)	287,000
Reclassification adjustment for items included in net income	(3,624,000)	(19,781,000)	(2,571,000)
Cumulative effect of change in accounting principle	0	0	872,000
Other comprehensive (loss) income	(16,447,000)	18,430,000	31,398,000
Comprehensive income	$ 96,474,000	$ 16,708,000	$ 82,732,000
Earnings (Loss) Per Share (Note 22)
Basic (loss) earnings per common share (in dollars per share)	$ 3.04	$ (0.04)	$ 1.21
Diluted (loss) earnings per common share (in dollars per share)	$ 3.01	$ (0.04)	$ 1.20