Financial Derivatives and Hedging Activities - Fair Value Amounts Recorded as Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Balance at January 1,	$ 1,882	$ (178)
Deferred (losses) gains on cash flow hedges	(6,990)	1,509
Reclassified to earnings	(532)	551
Balance at December 31,	$ (5,640)	$ 1,882