Net Product Sales by Geographic Region and Product Line - Schedule of Product Sales, Net by Geography (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Sales Information [Line Items]
Product sales, net	$ 38,413	$ 40,096
Percentage of product sales, net	100.00%	100.00%
United States [Member]
Sales Information [Line Items]
Product sales, net	36,608	37,457
Percentage of product sales, net	95.30%	93.40%
Total International [Member]
Sales Information [Line Items]
Product sales, net	1,805	2,639
Percentage of product sales, net	4.70%	6.60%
Total International [Member] | Europe [Member]
Sales Information [Line Items]
Product sales, net	582	1,040
Percentage of product sales, net	1.50%	2.60%
Total International [Member] | Asia Pacific [Member]
Sales Information [Line Items]
Product sales, net	$ 1,223	$ 1,599
Percentage of product sales, net	3.20%	4.00%