Derivative Instruments and Hedging Activities - Derivatives Not Designated as Hedging Instruments (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative, Notional Amount	$ 83,691		$ 83,691		$ 57,544
Derivative Assets, Fair Value	1,264		1,264		788
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	184		184		112
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	18	$ (10)	404	$ 225
Interest Rate Locks with Customers [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative, Notional Amount	38,965		38,965		27,007
Interest Rate Locks with Customers [Member] | Mortgage Banking Activities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	339	(109)	476	339
Interest Rate Locks with Customers [Member] | Other Assets [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets, Fair Value	1,264		1,264		788
Interest Rate Locks with Customers [Member] | Other Liabilities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0		0		0
Forward Loan Sale Commitments [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative, Notional Amount	44,726		44,726		30,537
Forward Loan Sale Commitments [Member] | Mortgage Banking Activities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(321)	$ 99	(72)	$ (114)
Forward Loan Sale Commitments [Member] | Other Assets [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets, Fair Value	0		0		0
Forward Loan Sale Commitments [Member] | Other Liabilities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 184		$ 184		$ 112