Carrying Amounts And Fair Values of Company's Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial Assets
Investments held-to-maturity	$ 225,994	$ 215,814
Other equity securities	36,412	33,636
Loans, net of allowance	2,622,588	2,488,171
Other assets	85,578	83,714
Financial Liabilities
Time Deposits	479,119	524,820
Securities sold under retail repurchase agreements and federal funds purchased	53,177	86,929
Advances from FHLB	520,000	405,058
Subordinated debentures	35,000	35,000
Financial Assets
Investments held-to-maturity	220,054	222,024
Other equity securities	36,412	33,636
Loans, net of allowance	2,587,170	2,453,314
Other assets	85,578	83,714
Financial Liabilities
Time Deposits	479,780	528,074
Securities sold under retail repurchase agreements and federal funds purchased	53,177	86,929
Advances from FHLB	550,662	451,408
Subordinated debentures	8,669	9,919
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets
Investments held-to-maturity	0	0
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	220,054	222,024
Other equity securities	36,412	33,636
Loans, net of allowance	0	0
Other assets	85,578	83,714
Financial Liabilities
Time Deposits	479,780	528,074
Securities sold under retail repurchase agreements and federal funds purchased	53,177	86,929
Advances from FHLB	550,662	451,408
Subordinated debentures	0	0
Significant Unobservable Inputs (Level 3)
Financial Assets
Investments held-to-maturity	0	0
Other equity securities	0	0
Loans, net of allowance	2,587,170	2,453,314
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	$ 8,669	$ 9,919