Financial Assets and Liabilities at Dates Indicated that Were Accounted for or Disclosed at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	$ 48,383	$ 36,149
Fair Value, Measurements, Recurring | U.S. Government Agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	130,897	156,428
Fair Value, Measurements, Recurring | State and Municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	173,423	174,491
Fair Value, Measurements, Recurring | Mortgage-Backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	457,544	490,479
Fair Value, Measurements, Recurring | Corporate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	2,007	1,996
Fair Value, Measurements, Recurring | Trust Preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	1,486	1,465
Fair Value, Measurements, Recurring | Marketable Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	723	723
Fair Value, Measurements, Recurring | Interest Rate Swap Agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	2,492	1,280
Other liabilities	(2,492)	(1,280)
Fair Value, Measurements, Recurring | Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	48,383	36,149
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Government Agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	130,897	156,428
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | State and Municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	173,423	174,491
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Mortgage-Backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	457,544	490,479
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	2,007	1,996
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Marketable Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	723	723
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Interest Rate Swap Agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	2,492	1,280
Other liabilities	(2,492)	(1,280)
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	48,383	36,149
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Trust Preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	$ 1,486	$ 1,465