Accumulated Other Comprehensive Loss - Net Change and Ending Balances for Various Components of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 161,761
Net Change	$ (1,158)	$ 4,003	(5,006)	$ 11,774
Ending Balance	150,783		150,783
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(11,932)	(22,973)
Cumulative effect of ASU 2016-01					$ 0
Balance at January 1, 2018, adjusted			(11,932)
Net Change			(4,801)	10,704
Ending Balance	(16,733)	(12,269)	(16,733)	(12,269)
Unrecognized Employee Benefit Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(34,196)	(38,636)
Cumulative effect of ASU 2016-01					0
Balance at January 1, 2018, adjusted			(34,196)
Net Change			569	688
Ending Balance	(33,627)	(37,948)	(33,627)	(37,948)
Unrealized Holding Gains on Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			632	59
Cumulative effect of ASU 2016-01					(632)
Balance at January 1, 2018, adjusted			0
Net Change			0	398
Ending Balance	0	457	0	457
Realized (Gains) Losses from Settlement of Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			739	551
Cumulative effect of ASU 2016-01					0
Balance at January 1, 2018, adjusted			739
Net Change			(774)	(16)
Ending Balance	(35)	535	(35)	535
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(44,757)	(60,999)
Cumulative effect of ASU 2016-01					$ (632)
Balance at January 1, 2018, adjusted			(45,389)
Net Change			(5,006)	11,774
Ending Balance	$ (50,395)	$ (49,225)	$ (50,395)	$ (49,225)