BUSINESS COMBINATIONS - Pro Forma Information (Details) - Bryn Mawr Bank Corporation Acquisition - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Business Acquisition [Line Items]
Net interest income	$ 137,632	$ 426,118
Provision for credit losses	(1,410)	(120,906)
Net interest income after provision for credit losses	139,042	547,024
Total noninterest income	65,200	202,847
Total noninterest expenses	134,514	398,107
Income before income taxes	69,728	351,764
Income tax provision	17,626	87,242
Net income	$ 52,102	$ 264,522
Per share data:
Weighted-average basic shares outstanding (in shares)	65,443,945	65,430,218
Dilutive shares (in shares)	282,516	297,071
Adjusted weighted-average diluted shares (in shares)	65,726,461	65,272,289
Basic earnings per common share (in dollars per share)	$ 0.80	$ 4.04
Diluted earnings per common share (in dollars per share)	$ 0.79	$ 4.03