FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 7,463,602	$ 6,840,632
Financial liabilities [Abstract]
Deposits	10,846,673	8,994,967
Overnight Federal Home Loan Bank borrowings	0	8,300
Securities sold under agreement to repurchase, short-term	168,491	241,708
Other Federal Home Loan Bank borrowings	7,704	3,750
Subordinated notes payable	13,755	13,795
Subordinated debt held by unconsolidated subsidiary trusts	79,382	77,320
Fair Value [Member]
Financial assets [Abstract]
Net loans	7,801,009	7,028,663
Financial liabilities [Abstract]
Deposits	10,864,309	8,997,551
Overnight Federal Home Loan Bank borrowings	0	8,300
Securities sold under agreement to repurchase, short-term	168,491	241,708
Other Federal Home Loan Bank borrowings	7,860	3,755
Subordinated notes payable	13,755	13,795
Subordinated debt held by unconsolidated subsidiary trusts	$ 79,382	$ 77,320