Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Product revenues	$ 235,853	$ 232,625	$ 728,498	$ 681,059
Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	100.00%	100.00%	100.00%	100.00%
United States
Segment Reporting Information [Line Items]
Product revenues	$ 104,033	$ 117,815	$ 337,697	$ 332,693
United States | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	44.00%	51.00%	46.00%	49.00%
China
Segment Reporting Information [Line Items]
Product revenues	$ 25,741	$ 21,573	$ 66,168	$ 57,983
China | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	11.00%	9.00%	9.00%	9.00%
Germany
Segment Reporting Information [Line Items]
Product revenues	$ 17,711	$ 17,670	$ 53,273	$ 54,261
Germany | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	8.00%	8.00%	7.00%	8.00%
South Korea
Segment Reporting Information [Line Items]
Product revenues	$ 16,569	$ 16,295	$ 50,714	$ 56,443
South Korea | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	7.00%	7.00%	7.00%	8.00%
Japan
Segment Reporting Information [Line Items]
Product revenues	$ 15,727	$ 10,532	$ 43,103	$ 32,545
Japan | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	7.00%	4.00%	6.00%	5.00%
Canada
Segment Reporting Information [Line Items]
Product revenues	$ 10,667	$ 9,440	$ 32,709	$ 28,513
Canada | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	5.00%	4.00%	5.00%	4.00%
Czech Republic
Segment Reporting Information [Line Items]
Product revenues	$ 9,175	$ 9,302	$ 29,826	$ 29,264
Czech Republic | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	4.00%	4.00%	4.00%	4.00%
United Kingdom
Segment Reporting Information [Line Items]
Product revenues	$ 8,143	$ 6,824	$ 26,250	$ 20,561
United Kingdom | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	3.00%	3.00%	4.00%	3.00%
Mexico
Segment Reporting Information [Line Items]
Product revenues	$ 5,706	$ 5,288	$ 16,398	$ 16,848
Mexico | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	2.00%	2.00%	2.00%	2.00%
Other
Segment Reporting Information [Line Items]
Product revenues	$ 22,381	$ 17,886	$ 72,360	$ 51,948
Other | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	9.00%	8.00%	10.00%	8.00%
Non U.S.
Segment Reporting Information [Line Items]
Product revenues	$ 131,820	$ 114,810	$ 390,801	$ 348,366
Non U.S. | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	56.00%	49.00%	54.00%	51.00%