Co-Promotion Agreement - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Co-Promotion Agreement [Line Items]
Promotion fee as a percentage gross margin	From the high single digits in 2014 to the low twenty percent levels in 2018.
Net payables	$ 10,756,000us-gaap_AccountsPayableCurrent	$ 8,525,000us-gaap_AccountsPayableCurrent
Kowa Pharmaceuticals America
Co-Promotion Agreement [Line Items]
Net receivable	600,000	600,000
Net payables	$ 700,000	$ 700,000
Kowa Pharmaceuticals America \| Minimum
Co-Promotion Agreement [Line Items]
Number of sales representatives	250

From the high single digits in 2014 to the low twenty percent levels in 2018.