FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 6,803,768	$ 6,231,837
Financial liabilities [Abstract]
Deposits	9,168,285	8,322,371
Short-term borrowings	0	54,400
Securities sold under agreement to repurchase, short-term	233,333	259,367
Other long-term debt	4,328	1,976
Subordinated notes payable	13,814	0
Subordinated debt held by unconsolidated subsidiary trusts	77,320	97,939
Fair Value [Member]
Financial assets [Abstract]
Net loans	6,971,242	6,247,939
Financial liabilities [Abstract]
Deposits	9,166,701	8,308,765
Short-term borrowings	0	54,400
Securities sold under agreement to repurchase, short-term	233,333	259,367
Other long-term debt	4,303	1,921
Subordinated notes payable	13,814	0
Subordinated debt held by unconsolidated subsidiary trusts	$ 77,320	$ 97,939