Derivative Instruments and Hedging Activities - Derivatives Not Designated as Hedging Instruments (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	$ 107,448	$ 73,995
Derivative Assets	1,058	1,089
Derivative Liabilities	74	102
Derivative instruments not designated as hedging instruments gain (loss), net	(164)	(311)	$ (330)
Interest Rate Swap [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	622
Interest Rate Swap [Member] | Other Assets [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets	0
Interest Rate Swap [Member] | Other Liabilities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liabilities	65
Credit Risk Contract [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	27,919
Credit Risk Contract [Member] | Other Noninterest Income [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	93	0	0
Credit Risk Contract [Member] | Other Assets [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets	0
Credit Risk Contract [Member] | Other Liabilities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liabilities	9
Interest Rate Locks with Customers [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	36,541	34,450
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	288	(301)	(467)
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	801	1,089
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 Liabilities	0	0
Forward Loan Sale Commitments [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	42,366	39,545
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	(359)	(10)	$ 137
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	257	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 Liabilities	$ 0	$ 102