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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Other Comprehensive Income on Derivatives	$ 1,162	$ (169)	$ 4,274	$ (1,080)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Other Comprehensive Income on Derivatives	$ 1,162	$ (169)	$ 4,274	$ (1,080)