BUSINESS COMBINATIONS - Pro Forma Information (Details) - Bryn Mawr Bank Corporation Acquisition $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) $ / shares shares
Business Acquisition [Line Items]
Net interest income	$ 149,613
Provision for loan and lease losses	(1,634)
Net interest income after provision for loan and lease losses	151,247
Total noninterest income	67,663
Total noninterest expenses	133,856
Income before income taxes	85,054
Income tax expense	20,454
Net income	$ 64,600
Per share data:
Weighted-average basic shares outstanding (in shares) | shares	65,426,291
Dilutive shares | shares	411,480
Adjusted weighted-average diluted shares (in shares) | shares	65,837,770
Basic earnings per common share (in dollars per share) | $ / shares	$ 0.99
Diluted earnings per common share (in dollars per share) | $ / shares	$ 0.98