Components of Other Income (Expense), Net (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Component Of Other Expense Income Nonoperating [Line Items]
Interest expense	$ (2,193)	$ (3,216)	$ (4,626)	$ (6,592)
Interest income on term deposits	171	93	217	225
Interest on income tax Refund	739		739
Gain on sale of mutual funds, net	513	329	875	560
Non-Service component of post-retirement benefit cost	(288)	(338)	(590)	(662)
Miscellaneous income	47	40	200	173
Other expense, net (See note 23)	$ (1,011)	$ (3,092)	$ (3,185)	$ (6,296)