Derivatives - Notional and Fair Values of Derivative Instruments on Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Notional Amounts	$ 752,936	$ 720,868
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	15,253	19,448
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	15,082	20,455
Derivatives designated as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts		140,000
Derivatives not designated as hedging instruments, Fair Value, Gross Liability		298
Derivatives designated as hedging instruments [Member] | Interest rate swap [Member] | Loss on Effective Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts		140,000
Derivatives designated as hedging instruments [Member] | Other liabilities [Member] | Interest rate swap [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Liability		298
Derivatives not designated as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	16,062	20,093
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	15,929	20,802
Derivatives not designated as hedging instruments [Member] | Interest rate swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts	661,421	547,477
Derivatives not designated as hedging instruments [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts	20,287
Derivatives not designated as hedging instruments [Member] | Forward Commitments To Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts	24,473	115,256
Derivatives not designated as hedging instruments [Member] | Interest Rate Lock Commitments On Residential Mortgage Loan [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts	12,814	58,135
Derivatives not designated as hedging instruments [Member] | Other liabilities [Member] | Interest rate swap [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	15,079	20,157
Derivatives not designated as hedging instruments [Member] | Other liabilities [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	3
Derivatives not designated as hedging instruments [Member] | Other liabilities [Member] | Forward Commitments To Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	355	590
Derivatives not designated as hedging instruments [Member] | Other liabilities [Member] | Interest Rate Lock Commitments On Residential Mortgage Loan [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	11	55
Derivatives not designated as hedging instruments [Member] | Other liabilities [Member] | Foreign exchange forward contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amounts	33,941
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	507
Derivatives not designated as hedging instruments, Fair Value, Gross Liability	481
Derivatives not designated as hedging instruments [Member] | Other assets [Member] | Interest rate swap [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	15,249	19,448
Derivatives not designated as hedging instruments [Member] | Other assets [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	4
Derivatives not designated as hedging instruments [Member] | Other assets [Member] | Forward Commitments To Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	51	190
Derivatives not designated as hedging instruments [Member] | Other assets [Member] | Interest Rate Lock Commitments On Residential Mortgage Loan [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, Fair Value, Gross Assets	$ 251	$ 455