Derivative Instruments and Hedging Activities - Fair Value of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	$ 208	$ 192
Derivative Liabilities, Fair Value, Gross Liability	12,938	9,703
Other Assets [Member] | Derivative Designated as Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	0	0
Other Assets [Member] | Derivative Designated as Cash Flow Hedges [Member] | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	0	0
Other Assets [Member] | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	8,810	7,552
Other Assets [Member] | Not Designated as Hedging Instrument | Residential Mortgage Loan Commitments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	87	43
Other Assets [Member] | Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	8,515	7,332
Other Assets [Member] | Not Designated as Hedging Instrument | Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value, Gross Asset	208	177
Other Liabilities [Member] | Derivative Designated as Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value, Gross Liability	3,891	1,945
Other Liabilities [Member] | Derivative Designated as Cash Flow Hedges [Member] | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value, Gross Liability	3,891	1,945
Other Liabilities [Member] | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value, Gross Liability	9,047	7,771
Other Liabilities [Member] | Not Designated as Hedging Instrument | Residential Mortgage Loan Commitments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value, Gross Liability	0	0
Other Liabilities [Member] | Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value, Gross Liability	9,047	7,771
Other Liabilities [Member] | Not Designated as Hedging Instrument | Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value, Gross Liability	$ 0	$ 0