Changes In Accumulated Other Comprehensive Income (Loss) - Changes within Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 273,456	$ 245,225	$ 212,599
Other comprehensive income (loss)	27,085	(13,934)	(10,971)
Amounts reclassified from accumulated other comprehensive loss	717	569	547
Ending balance	353,396	273,456	245,225
Total Accumulated Other Comprehensive (Loss) Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(47,950)	(34,585)	(24,161)
Ending balance	(20,148)	(47,950)	(34,585)
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(27,885)	(16,920)	(6,586)
Other comprehensive income (loss)	25,664	(10,965)	(10,334)
Amounts reclassified from accumulated other comprehensive loss	0		0
Ending balance	(2,221)	(27,885)	(16,920)
Defined Benefit Pension Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(20,065)	(17,665)	(17,575)
Other comprehensive income (loss)	1,299	(2,969)	(637)
Amounts reclassified from accumulated other comprehensive loss	717	569	547
Ending balance	(18,049)	(20,065)	(17,665)
Gains and Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	0	0
Other comprehensive income (loss)	122	0	0
Amounts reclassified from accumulated other comprehensive loss		0	0
Ending balance	$ 122	$ 0	$ 0