Derivative Instruments and Hedging Activities - Derivatives Designated as Hedging Instruments (Detail) - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	$ 19,612		$ 19,612		$ 19,993
Derivative Assets	0		0		0
Derivative Liabilities	226		226		254
Net loss	(34)	$ (80)	(102)	$ (161)
Gain (loss) recognized in other comprehensive income (loss)	(127)	(141)
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	18,204		18,204		18,566
Gain (loss) recognized in other comprehensive income (loss)	(127)	(141)
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net loss	36	80	107	161
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Other Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets	0		0		0
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities	195		195		217
Interest Rate Swap [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	1,408		1,408		1,427
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Other Noninterest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net loss	2	$ 0	5	$ 0
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Other Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Assets	0		0		0
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Other Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Liabilities	$ 31		$ 31		$ 37