LOANS (Loans Held to Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	$ 10,023,051	$ 8,367,917
Allowance for credit losses	(131,606)	(70,395)	$ (61,963)	$ (55,686)
Loans receivable, net	9,891,445	8,297,522
Commercial and industrial | Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	2,534,799	2,530,809
Allowance for credit losses	(38,818)	(34,207)	(29,958)
Commercial and industrial | Paycheck Protection Program ("PPP")
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	957,785	0
Allowance for credit losses	0	0	0
Commercial and industrial | Owner occupied commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	1,776,406	1,472,704
Allowance for credit losses	(20,001)	(7,921)	(6,247)
Commercial and industrial | Non-owner occupied commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	1,921,481	1,495,877
Allowance for credit losses	(20,873)	(7,584)	(7,182)
Commercial and industrial | Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	863,220	1,027,081
Allowance for credit losses	(20,080)	(8,677)	(6,707)
Agricultural and agricultural real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	714,526	565,837
Allowance for credit losses	(7,129)	(5,680)	(4,916)
Residential real estate
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	840,442	832,277
Allowance for credit losses	(11,935)	(1,504)	(1,813)
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans receivable held to maturity	414,392	443,332
Allowance for credit losses	$ (12,770)	$ (4,822)	$ (5,140)