BUSINESS COMBINATIONS - Pro Forma Information (Details) - BMBC $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares shares
Business Acquisition [Line Items]
Net interest income	$ 567,183
(Recovery of) provision for credit losses	(115,212)
Net interest income after provision for credit losses	682,395
Total noninterest income	271,576
Total noninterest expenses	556,524
Income before income taxes	397,447
Income tax provision	100,009
Net income	$ 297,438
Per share data:
Weighted-average basic shares outstanding (in shares) | shares	65,445,251
Dilutive shares (in shares) | shares	332,765
Adjusted weighted-average diluted shares (in shares) | shares	65,778,016
Basic earnings per common share (in dollars per share) | $ / shares	$ 4.54
Diluted earnings per common share (in dollars per share) | $ / shares	$ 4.52