Derivative Instruments and Hedging Activities - Effect of Derivative Financial Instruments on Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Cash Flow Hedges | Interest Expense | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ (1,464)	$ 426	$ (2,353)	$ (196)
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	0	0
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Income (Loss) Recognized in Earnings	242	24	944	342
Not Designated as Hedging Instrument | Other Non-interest Income | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Income (Loss) Recognized in Earnings	192	47	902	686
Not Designated as Hedging Instrument | Other Non-interest Income | Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Income (Loss) Recognized in Earnings	51	(4)	15	(139)
Not Designated as Hedging Instrument | Mortgage Banking Income | Residential Mortgage Loan Commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Income (Loss) Recognized in Earnings	$ (1)	$ (19)	$ 27	$ (205)