Derivatives and Hedging Activities - Summary of Effect of Company's Derivative Financial Instruments That Are Not Designated as Hedging Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Derivative Instruments Gain Loss [Line Items]
Gain or (loss) recognized in income on derivative	$ (4)	$ (4)
Interest Rate Products [Member] | Other income (expense) [Member]
Derivative Instruments Gain Loss [Line Items]
Gain or (loss) recognized in income on derivative	(4)	(4)
Fee Income | Other income (expense) [Member]
Derivative Instruments Gain Loss [Line Items]
Gain or (loss) recognized in income on derivative	$ 31	$ 31