Summary of Amount of Gain (Loss) Recognized in AOCI in Consolidated Statements of Comprehensive Income Related to Company's Derivative Assets and Liabilities (Detail) - Derivatives Designated as Hedging Instruments [Member] - Cash Flow Hedging [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Other Comprehensive Income on Derivatives	$ 910	$ (1,157)	$ 3,112	$ (911)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Other Comprehensive Income on Derivatives	$ 910	$ (1,157)	$ 3,112	$ (911)