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DERIVATIVE FINANCIAL INSTRUMENTS - Fair Value of Derivative Instruments (Details) $ in Thousands	Sep. 30, 2020 USD ($)	Apr. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) instrument
Derivative [Line Items]
Notional	$ 880,178		$ 502,172
Total derivatives	(15,107)		966
Designated as Hedging Instrument
Derivative [Line Items]
Notional			75,000
Total derivatives		$ 1,300
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional			427,172
Derivative Liability			1,725
Other liabilities \| Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability			(759)
Interest rate products \| Other assets \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	65,068		71,804
Derivative Asset	6,339		$ 2,520
Interest rate products \| Other liabilities \| Designated as Hedging Instrument
Derivative [Line Items]
Count \| instrument			3
Notional			$ 75,000
Derivative Liability			(759)
Interest rate products \| Other liabilities \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	65,068		71,804
Derivative Liability	(7,067)		(2,688)
Risk participation agreements \| Other liabilities \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	4,410		4,524
Derivative Liability	(12)		(4)
Interest rate lock commitments with customers \| Other assets \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	308,807		99,057
Derivative Asset	11,606		1,768
Interest rate lock commitments with customers \| Other liabilities \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	22,134		28,505
Derivative Liability	(174)		(191)
Forward sale commitments \| Other assets \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	56,290		61,301
Derivative Asset	503		596
Forward sale commitments \| Other liabilities \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	245,224		90,177
Derivative Liability	(1,097)		$ (276)
Financial derivatives related to sales of certain Visa Class B shares \| Other liabilities \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional	113,177
Derivative Liability	$ (25,205)