Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Postretirement Benefit Plan | UNITED STATES
Net periodic benefit cost
Service cost	$ 1	$ 1	$ 2	$ 2
Interest cost	81	88	162	176
Net amortization/deferrals	(76)	(73)	(152)	(146)
Net periodic benefit cost (credit)	6	16	$ 12	$ 32
Assumptions
Discount Rate			3.43%	3.76%
Other Postretirement Benefit Plan | Foreign Plan
Net periodic benefit cost
Service cost	8	7	$ 16	$ 14
Interest cost	26	24	52	48
Net amortization/deferrals	(4)	(7)	(8)	(14)
Net periodic benefit cost (credit)	30	24	$ 60	$ 48
Assumptions
Discount Rate			3.21%	3.46%
Pension Plan | UNITED STATES
Net periodic benefit cost
Service cost	87	86	$ 174	$ 172
Interest cost	333	356	666	712
Expected return on plan assets	(445)	(433)	(890)	(866)
Net amortization/deferrals	243	248	486	496
Net periodic benefit cost (credit)	218	257	$ 436	$ 514
Assumptions
Discount Rate			3.56%	3.95%
Expected long-term rate of return			5.15%	4.95%
Rate of compensation increase			3.00%	3.00%
Pension Plan | Foreign Plan
Net periodic benefit cost
Service cost	691	614	$ 1,382	$ 1,228
Interest cost	1,834	1,677	3,668	3,354
Expected return on plan assets	(3,466)	(2,910)	(6,932)	(5,820)
Net amortization/deferrals	554	685	1,108	1,370
Net periodic benefit cost (credit)	$ (387)	$ 66	$ (774)	$ 132
Assumptions
Discount Rate			2.40%	2.51%
Expected long-term rate of return			5.10%	4.93%
Rate of compensation increase			2.60%	2.54%