Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income (loss) before attribution of noncontrolling interest	$ 110,311	$ (1,722)	$ 51,334
Net loss attributable to noncontrolling interest	(2,610)	0	0
Net income (loss) attributable to Amerant Bancorp Inc.	$ 112,921	$ (1,722)	$ 51,334
Denominator:
Basic weighted averages shares outstanding (in shares)	37,169	41,737	42,543
Dilutive effect of shared-based compensation awards (in shares)	359	0	396
Diluted weighted average shares outstanding (in shares)	37,528	41,737	42,939
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
Antidilutive securities excluded from computation	462,302	248,750	530,620