Segment Reporting (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Product revenues	$ 1,038,259	$ 985,683	$ 917,600
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Total product revenues in percentage	100.00%	100.00%	100.00%
Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	100.00%	100.00%	100.00%
United States
Segment Reporting Information [Line Items]
Product revenues	$ 488,926	$ 454,669	$ 449,065
United States | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	47.00%	46.00%	49.00%
China
Segment Reporting Information [Line Items]
Product revenues	$ 93,628	$ 93,645	$ 80,493
China | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	9.00%	9.00%	9.00%
Germany
Segment Reporting Information [Line Items]
Product revenues	$ 88,366	$ 71,768	$ 70,258
Germany | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	9.00%	7.00%	8.00%
South Korea
Segment Reporting Information [Line Items]
Product revenues	$ 58,717	$ 64,715	$ 75,396
South Korea | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	6.00%	7.00%	8.00%
Japan
Segment Reporting Information [Line Items]
Product revenues	$ 62,633	$ 57,467	$ 45,103
Japan | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	6.00%	6.00%	5.00%
Canada
Segment Reporting Information [Line Items]
Product revenues	$ 44,500	$ 46,368	$ 37,954
Canada | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	4.00%	5.00%	4.00%
Czech Republic
Segment Reporting Information [Line Items]
Product revenues	$ 42,665	$ 38,828	$ 38,164
Czech Republic | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	4.00%	4.00%	4.00%
United Kingdom
Segment Reporting Information [Line Items]
Product revenues	$ 37,533	$ 36,033	$ 28,540
United Kingdom | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	4.00%	4.00%	3.00%
Romania
Segment Reporting Information [Line Items]
Product revenues	$ 22,435	$ 18,050	$ 11,907
Romania | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	2.00%	2.00%	1.00%
Other
Segment Reporting Information [Line Items]
Product revenues	$ 98,856	$ 104,320	$ 80,720
Other | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	9.00%	10.00%	9.00%
Non U.S.
Segment Reporting Information [Line Items]
Product revenues	$ 549,333	$ 531,014	$ 468,535
Non U.S. | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	53.00%	54.00%	51.00%