Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Product revenues	$ 263,779	$ 243,378	$ 525,668	$ 492,645
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	$ 123,512	$ 114,141	$ 243,862	$ 233,664
United States | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	47.00%	47.00%	46.00%	47.00%
China
Segment Reporting Information [Line Items]
Product revenues	$ 24,927	$ 19,962	$ 49,131	$ 40,427
China | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	9.00%	8.00%	9.00%	8.00%
Germany
Segment Reporting Information [Line Items]
Product revenues	$ 23,626	$ 17,694	$ 45,988	$ 35,562
Germany | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	9.00%	7.00%	9.00%	7.00%
South Korea
Segment Reporting Information [Line Items]
Product revenues	$ 15,783	$ 17,754	$ 29,605	$ 34,145
South Korea | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	6.00%	7.00%	6.00%	7.00%
Japan
Segment Reporting Information [Line Items]
Product revenues	$ 13,275	$ 13,093	$ 26,848	$ 27,376
Japan | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	5.00%	5.00%	5.00%	6.00%
Canada
Segment Reporting Information [Line Items]
Product revenues	$ 12,590	$ 11,113	$ 25,703	$ 22,042
Canada | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	5.00%	5.00%	5.00%	5.00%
Czech Republic
Segment Reporting Information [Line Items]
Product revenues	$ 11,106	$ 9,944	$ 22,821	$ 20,651
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	$ 8,467	$ 8,439	$ 19,312	$ 18,107
United Kingdom | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	3.00%	4.00%	4.00%	4.00%
Mexico
Segment Reporting Information [Line Items]
Product revenues	$ 4,848	$ 5,322	$ 11,146	$ 10,692
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	$ 25,645	$ 25,916	$ 51,252	$ 49,979
Other | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	10.00%	11.00%	10.00%	10.00%
Non U.S.
Segment Reporting Information [Line Items]
Product revenues	$ 140,267	$ 129,237	$ 281,806	$ 258,981
Non U.S. | Sales Revenue, Net | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Total product revenues in percentage	53.00%	53.00%	54.00%	53.00%