Condensed Unconsolidated Holding Companies’ Financial Statements - Income Statement Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income
Interest	$ 247,844	$ 260,554	$ 312,974
Expenses
Interest expense	42,703	71,002	99,886
Reversal of (provision for) loan losses	(16,500)	88,620	(3,150)
Other expenses	11,741	7,727	15,420
Income (loss) before income tax (expense) benefit	144,020	(4,334)	64,031
Income tax benefit	(33,709)	2,612	(12,697)
Net income (loss) attributable to Amerant Bancorp Inc.	112,921	(1,722)	51,334
Mercantil Bank Holding Corporation | Parent Company | Reportable Legal Entities
Income
Interest	117	265	40
Equity in earnings of subsidiary	120,253	2,520	56,755
Total income	120,370	2,785	56,795
Expenses
Interest expense	3,766	1,968	0
Other expenses	6,082	3,688	7,434
Total expense	9,848	5,656	7,434
Income (loss) before income tax (expense) benefit	110,522	(2,871)	49,361
Income tax benefit	2,399	1,148	1,973
Net income (loss) attributable to Amerant Bancorp Inc.	112,921	(1,723)	51,334
Mercantil Florida Bancorp, Inc | Subsidiaries | Reportable Legal Entities
Income
Interest	41	102	152
Equity in earnings of subsidiary	122,311	4,810	62,979
Other income	0	0	6
Total income	122,352	4,912	63,137
Expenses
Interest expense	2,451	2,533	7,184
Reversal of (provision for) loan losses	0	0	0
Other expenses	263	444	726
Total expense	2,714	2,977	7,910
Income (loss) before income tax (expense) benefit	119,638	1,935	55,227
Income tax benefit	616	585	1,528
Net income (loss) attributable to Amerant Bancorp Inc.	$ 120,254	$ 2,520	$ 56,755