NONINTEREST INCOME - Investment Management and Fiduciary Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Trust fees
Revenue from External Customer [Line Items]
Noninterest fee income	$ 9,764	$ 6,954
Wealth management and advisory fees
Revenue from External Customer [Line Items]
Noninterest fee income	4,489	4,008
Investment management and fiduciary income
Revenue from External Customer [Line Items]
Noninterest fee income	$ 14,253	$ 10,962