Derivative Instruments and Hedging Activities - Effect of Derivative Financial Instruments on Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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)	$ 279	$ (1,054)	$ (889)	$ (622)
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	505	83	702	317
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	588	118	710	638
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	(66)	14	(36)	(135)
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	$ (17)	$ (49)	$ 28	$ (186)