Fair Value Measurement of Assets and Liabilities - Assets and Liabilities Measured at Fair Value on Recurring and Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	$ 758,421	$ 829,692
Trading securities	14,186	14,264
Loans held for sale		0
U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	92,996	84,665
U.S. Government Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	45,014	48,627
Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	37,615	37,700
Residential Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	459,577	508,029
Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	21,244	19,215
Corporate and Other Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	77,915	83,398
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	24,060	48,058
Fair Value [Member] | Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	758,421	829,692
Trading securities	14,186	14,264
Loans held for sale	3,351	10,488
Other assets	14,931	15,122
Total assets	790,889
Other liabilities	23,639	20,586
Total Liabilities Fair Value Disclosure		20,586
Total liabilities	23,639
Total Assets Fair Value Disclosure		869,566
Fair Value [Member] | Recurring Fair Value Measurements [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	92,996	84,665
Fair Value [Member] | Recurring Fair Value Measurements [Member] | U.S. Government Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	45,014	48,627
Fair Value [Member] | Recurring Fair Value Measurements [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	37,615	37,700
Fair Value [Member] | Recurring Fair Value Measurements [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	459,577	508,029
Fair Value [Member] | Recurring Fair Value Measurements [Member] | Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	21,244	19,215
Fair Value [Member] | Recurring Fair Value Measurements [Member] | Corporate and Other Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	77,915	83,398
Fair Value [Member] | Recurring Fair Value Measurements [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	24,060	48,058
Fair Value [Member] | Non-Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	7,350
Collateral dependent impaired loans	11,931	35,700
Loan servicing rights	2,130	3,677
Foreclosed assets	12,433	25,929
Total	33,844
Non Recurring Fair Value Measurements Asset Liability Total		65,306
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	116,863	138,843
Trading securities	0	0
Loans held for sale	0	0
Other assets	0	0
Total assets	116,863
Other liabilities	0	0
Total Liabilities Fair Value Disclosure		0
Total liabilities	0
Total Assets Fair Value Disclosure		138,843
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	92,996	84,665
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | U.S. Government Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | Corporate and Other Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	21,620	27,273
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Fair Value Measurements [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	2,247	26,905
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Non-Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	0
Collateral dependent impaired loans	0	0
Loan servicing rights	0	0
Foreclosed assets	0	0
Total	0
Non Recurring Fair Value Measurements Asset Liability Total		0
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	615,857	662,326
Trading securities	14,186	14,264
Loans held for sale	3,351	10,488
Other assets	14,931	15,122
Total assets	648,325
Other liabilities	23,639	20,586
Total Liabilities Fair Value Disclosure		20,586
Total liabilities	23,639
Total Assets Fair Value Disclosure		702,200
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | U.S. Government Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	45,014	48,627
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	37,615	37,700
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	438,601	483,277
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	16,519	15,444
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | Corporate and Other Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	56,295	56,125
Significant Other Observable Inputs (Level 2) [Member] | Recurring Fair Value Measurements [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	21,813	21,153
Significant Other Observable Inputs (Level 2) [Member] | Non-Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	7,350
Collateral dependent impaired loans	0	0
Loan servicing rights	0	0
Foreclosed assets	0	0
Total	7,350
Non Recurring Fair Value Measurements Asset Liability Total		0
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	25,701	28,523
Trading securities		0
Loans held for sale	0	0
Other assets	0	0
Total assets	25,701
Other liabilities	0	0
Total Liabilities Fair Value Disclosure		0
Total liabilities	0
Total Assets Fair Value Disclosure		28,523
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | U.S. Government Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	20,976	24,752
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	4,725	3,771
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | Corporate and Other Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Significant Unobservable Inputs (Level 3) [Member] | Recurring Fair Value Measurements [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0	0
Significant Unobservable Inputs (Level 3) [Member] | Non-Recurring Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	0
Collateral dependent impaired loans	11,931	35,700
Loan servicing rights	2,130	3,677
Foreclosed assets	12,433	25,929
Total	26,494
Non Recurring Fair Value Measurements Asset Liability Total		$ 65,306