Acquisitions and Divestitures - Pro Forma (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Net interest income, Actual	$ 222,912
Non-interest income, Actual	89,510
Net interest income	(41,750)
IBERIABANK (IBKC)
Business Acquisition [Line Items]
Net interest income	550,636	$ 566,174	$ 1,691,623	$ 1,711,502
Noninterest income	290,773	235,409	783,132	645,781
Net income (loss)	$ 71,162	$ 218,572	$ 359,214	$ 654,884