Summary of Amount of Gain or Loss Recognized in Other Non-Interest Expense in Consolidated Statements of Income Related to Derivative Assets and Liabilities (Detail) - Interest Rate Products [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments	$ (440)	$ 20	$ (792)	$ (86)
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments	(1)	7	(2)	2
Derivatives Designated as Hedging Instruments [Member] | Fair value adjustments on derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments	(138)	121	(331)	6
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments	$ 137	$ (114)	$ 329	$ (4)