NONINTEREST INCOME - Investment Management and Fiduciary Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Trust fees
Revenue from External Customer [Line Items]
Noninterest fee income	$ 7,308	$ 6,685	$ 14,262	$ 13,250
Wealth management and advisory fees
Revenue from External Customer [Line Items]
Noninterest fee income	3,621	3,697	7,629	7,279
Investment management and fiduciary income
Revenue from External Customer [Line Items]
Noninterest fee income	$ 10,929	$ 10,382	$ 21,891	$ 20,529