REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Deferred revenue related to fixed fee contracts	$ 6,100				$ 6,500				$ 6,100	$ 6,500
Disaggregation of Revenue [Line Items]
Other non-interest income not within the scope of ASC 606									11,816	12,822	$ 24,541
Total fees and other income	$ 26,656	$ 23,045	$ 22,662	$ 21,521	$ 26,793	$ 25,126	$ 24,380	$ 25,248	93,884	101,547	149,997
Fees and Other Income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									82,068	88,725	125,456
Wealth management and trust fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									72,888	75,757	99,818
Investment management fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									6,261	10,155	21,728
Other income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									$ 2,919	$ 2,813	$ 3,910