Fair Value Measurements of Financial Assets and Liabilities on Recurring and Non Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Liabilities:
Derivative instruments	$ (1,933)	$ (2,537)
Total fair value	(1,933)	(2,537)
Fair Value, Inputs, Level 2
Liabilities:
Derivative instruments	(1,933)	(2,537)
Total fair value	$ (1,933)	$ (2,537)