Carrying Amounts And Fair Values of Company's Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financial Assets
Investments held-to-maturity	$ 226,457	$ 215,814
Other equity securities	37,312	33,636
Loans, net of allowance	2,566,443	2,488,171
Other assets	84,949	83,714
Financial Liabilities
Time Deposits	487,571	524,820
Securities sold under retail repurchase agreements and federal funds purchased	54,731	86,929
Advances from FHLB	540,000	405,058
Subordinated debentures	35,000	35,000
Financial Assets
Investments held-to-maturity	220,838	222,024
Other equity securities	37,312	33,636
Loans, net of allowance	2,609,329	2,453,314
Other assets	84,949	83,714
Financial Liabilities
Time Deposits	489,080	528,074
Securities sold under retail repurchase agreements and federal funds purchased	54,731	86,929
Advances from FHLB	570,955	451,408
Subordinated debentures	8,855	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	220,838	255,660
Other equity securities	37,312	33,636
Loans, net of allowance	0	0
Other assets	84,949	83,714
Financial Liabilities
Time Deposits	489,080	528,074
Securities sold under retail repurchase agreements and federal funds purchased	54,731	86,929
Advances from FHLB	570,955	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	2,609,329	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	$ 8,855	$ 9,919