FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 6,231,837	$ 6,209,174
Financial liabilities [Abstract]
Deposits	8,322,371	8,444,420
Short-term borrowings	54,400	24,000
Securities sold under agreement to repurchase, short-term	259,367	337,011
Other long-term debt	1,976	2,071
Subordinated debt held by unconsolidated subsidiary trusts	97,939	122,814
Fair Value [Member]
Financial assets [Abstract]
Net loans	6,247,939	6,244,941
Financial liabilities [Abstract]
Deposits	8,308,765	8,431,481
Short-term borrowings	54,400	24,000
Securities sold under agreement to repurchase, short-term	259,367	337,011
Other long-term debt	1,921	2,021
Subordinated debt held by unconsolidated subsidiary trusts	$ 97,939	$ 122,814