DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Effect of cash flow hedging and fair value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Loans
Derivative Instruments, Gain (Loss) [Line Items]
Income and expense line items presented in the consolidated statements of income	$ 25,094	$ 25,918	$ 72,490	$ 80,398
Securities and other
Derivative Instruments, Gain (Loss) [Line Items]
Income and expense line items presented in the consolidated statements of income	3,821	4,557	11,792	15,006
Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Income and expense line items presented in the consolidated statements of income	1,555	3,869	7,109	14,437
Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Income and expense line items presented in the consolidated statements of income	1,778	1,941	5,415	7,149
Non-interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Income and expense line items presented in the consolidated statements of income	11,350	10,102	31,103	28,233
Interest rate swap on wholesale funding | Cash flow hedges | Deposits
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges:		(365)		(580)
Interest rate swap on wholesale funding | Cash flow hedges | Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges:	(205)	(62)	(589)	(62)
Interest rate swap on variable rate loans | Cash flow hedges | Loans
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges:	92		189
Interest rate swap on securities | Fair value hedges | Securities and other
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on fair value hedges:	$ (144)	$ (204)	$ (421)	$ (145)