FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 6,234,760	$ 6,231,837
Financial liabilities [Abstract]
Deposits	8,488,205	8,322,371
Short-term borrowings	0	54,400
Securities sold under agreement to repurchase, short-term	142,359	259,367
Other long-term debt	1,931	1,976
Subordinated debt held by unconsolidated subsidiary trusts	97,939	97,939
Fair Value [Member]
Financial assets [Abstract]
Net loans	6,349,252	6,247,939
Financial liabilities [Abstract]
Deposits	8,481,874	8,308,765
Short-term borrowings	0	54,400
Securities sold under agreement to repurchase, short-term	142,359	259,367
Other long-term debt	1,922	1,921
Subordinated debt held by unconsolidated subsidiary trusts	$ 97,939	$ 97,939