Summary of Amount of Gain (Loss) Recognized in Other Non-Interest Expense in Consolidated Statements of Income Related to Derivative Assets and Liabilities (Detail) - Interest Rate Swap [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized	$ (873)	$ 336
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized	1
Derivatives Designated as Hedging Instruments [Member] | Fair value adjustments on derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized	(58)	81
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized	$ 59	$ (81)