Derivative Instruments and Hedging Activities - Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value	$ 0	$ 192
Derivative Liabilities, Fair Value	16,951	9,703
Other Assets | Derivative Designated as Cash Flow Hedges | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value	0	0
Other Assets | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value	10,938	7,552
Other Assets | Not Designated as Hedging Instrument | Residential Mortgage Loan Commitments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value	70	43
Other Assets | Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value	10,676	7,332
Other Assets | Not Designated as Hedging Instrument | Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets, Fair Value	192	177
Other Liabilities | Derivative Designated as Cash Flow Hedges | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value	5,786	1,945
Other Liabilities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value	11,165	7,771
Other Liabilities | Not Designated as Hedging Instrument | Residential Mortgage Loan Commitments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value	0	0
Other Liabilities | Not Designated as Hedging Instrument | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value	11,165	7,771
Other Liabilities | Not Designated as Hedging Instrument | Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities, Fair Value	$ 0	$ 0