FAIR VALUE (Carrying Amounts and Fair Values of Company's Financial Instruments) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Liabilities
Securities sold under retail repurchase agreements and federal funds purchased	$ 124,205	$ 109,145
Advances from FHLB	550,000	685,000
Subordinated debentures	30,000	35,000
Reported Value Measurement [Member]
Financial Assets
Investments held-to-maturity and other equity securities	35,829	249,601
Loans, net of allowance	3,736,565	3,454,475
Other assets	92,711	90,866
Financial Liabilities
Time Deposits	576,716	508,444
Securities sold under retail repurchase agreements and federal funds purchased	124,205	109,145
Advances from FHLB	550,000	685,000
Subordinated debentures	30,000	35,000
Estimate of Fair Value Measurement [Member]
Financial Assets
Investments held-to-maturity and other equity securities	35,829	253,040
Loans, net of allowance	3,769,922	3,526,807
Other assets	92,711	90,866
Financial Liabilities
Time Deposits	578,905	508,000
Securities sold under retail repurchase agreements and federal funds purchased	124,205	109,145
Advances from FHLB	566,191	704,410
Subordinated debentures	14,505	14,694
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets
Investments held-to-maturity and other equity securities	0	0
Loans, net of allowance	0	0
Other assets	0	0
Financial Liabilities
Time Deposits	0	0
Securities sold under retail repurchase agreements and federal funds purchased	0	0
Advances from FHLB	0	0
Subordinated debentures	0	0
Significant Other Observable Inputs (Level 2)
Financial Assets
Investments held-to-maturity and other equity securities	35,829	253,040
Loans, net of allowance	0	0
Other assets	92,711	90,866
Financial Liabilities
Time Deposits	578,905	508,000
Securities sold under retail repurchase agreements and federal funds purchased	124,205	109,145
Advances from FHLB	566,191	704,410
Subordinated debentures	0	0
Significant Unobservable Inputs (Level 3)
Financial Assets
Investments held-to-maturity and other equity securities	0	0
Loans, net of allowance	3,769,922	3,526,807
Other assets	0	0
Financial Liabilities
Time Deposits	0	0
Securities sold under retail repurchase agreements and federal funds purchased	0	0
Advances from FHLB	0	0
Subordinated debentures	$ 14,505	$ 14,694