ACQUISITIONS (Pro Forma Information (unaudited)) (Details) - AIM Bancshares, Inc. - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Net interest income	$ 557,166	$ 491,462
Net income available to common stockholders	$ 167,168	$ 170,010
Basic earnings per share (in dollars per share)	$ 3.94	$ 4.13
Diluted earnings per share (in dollars per share)	$ 3.93	$ 4.12