Co-Promotion Agreement - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) Employee	Dec. 31, 2015 USD ($)
Co-Promotion Agreement [Line Items]
Accrued expenses and other current liabilities	$ 37,720	$ 24,226
Co-Promotion Agreement (the Agreement)
Co-Promotion Agreement [Line Items]
Promotion fee as a percentage of gross margin	19.00%	15.00%
Promotion fee as a percentage gross margin	Scheduled to increase to low twenty percent levels in 2017 and 2018, subject to certain adjustments.
Co-Promotion Agreement (the Agreement) | Kowa Pharmaceuticals America
Co-Promotion Agreement [Line Items]
Accrued expenses and other current liabilities	$ 2,500	$ 2,500
Co-Promotion Agreement (the Agreement) | Kowa Pharmaceuticals America | Minimum
Co-Promotion Agreement [Line Items]
Number of sales representatives | Employee	250