NONINTEREST INCOME - Investment Management and Fiduciary Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Trust fees
Revenue from External Customer [Line Items]
Noninterest fee income	$ 10,808	$ 7,308	$ 20,572	$ 14,262
Wealth management and advisory fees
Revenue from External Customer [Line Items]
Noninterest fee income	4,552	3,621	9,041	7,629
Investment management and fiduciary income
Revenue from External Customer [Line Items]
Noninterest fee income	$ 15,360	$ 10,929	$ 29,613	$ 21,891