GOODWILL AND OTHER INTANGIBLE ASSETS--Schedule of Other Intangibles (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 100,544	$ 100,544
Finite-Lived Intangible Assets, Accumulated Amortization	$ (33,125)	(24,343)
Core deposits
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization method	accelerated basis
Finite-Lived Intangible Assets, Gross	$ 51,031	51,031
Finite-Lived Intangible Assets, Accumulated Amortization	$ (25,930)	(21,149)
Customer lists
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization method	straight-line basis
Finite-Lived Intangible Assets, Gross	$ 39,420	39,420
Finite-Lived Intangible Assets, Accumulated Amortization	(3,883)	(1,195)
Other
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	10,093	10,093
Finite-Lived Intangible Assets, Accumulated Amortization	$ (3,312)	$ (1,999)