Carrying Amounts And Fair Values of Company's Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financial Assets
Investments held-to-maturity and other equity securities	$ 249,450	$ 213,398
Loans, net of allowance	2,488,171	2,190,266
Accrued interest receivable and other assets	83,714	81,098
Financial Liabilities
Time Deposits	524,820	584,321
Securities sold under retail repurchase agreements and federal funds purchased	86,929	143,613
Advances from FHLB	405,058	405,408
Subordinated debentures	35,000	35,000
Financial Assets
Investments held-to-maturity and other equity securities	255,660	219,100
Loans, net of allowance	2,453,314	2,276,333
Accrued interest receivable and other assets	83,714	81,098
Financial Liabilities
Time Deposits	528,074	588,818
Securities sold under retail repurchase agreements and federal funds purchased	86,929	143,613
Advances from FHLB	451,408	452,378
Subordinated debentures	9,919	9,810
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
Accrued interest receivable and 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	255,660	219,100
Loans, net of allowance	0	0
Accrued interest receivable and other assets	83,714	81,098
Financial Liabilities
Time Deposits	528,074	588,818
Securities sold under retail repurchase agreements and federal funds purchased	86,929	143,613
Advances from FHLB	451,408	452,378
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	2,453,314	2,276,333
Accrued interest receivable and 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	$ 9,919	$ 9,810