Helsinn License Agreement - Additional Information (Detail) - USD ($)	Mar. 31, 2017	Aug. 31, 2016
Potential Regulatory and Sales-Based Milestone Payment | Maximum
Related Party Transaction [Line Items]
Milestone payment receivable amount		$ 444,000,000
Helsinn License Agreement | Helsinn
Related Party Transaction [Line Items]
Compensation receivable for grant of rights		20,000,000
Helsinn License Agreement | Helsinn | Payment in August 2016
Related Party Transaction [Line Items]
Compensation receivable for grant of rights		$ 15,000,000
Helsinn License Agreement | Helsinn | Balance Payment
Related Party Transaction [Line Items]
Compensation receivable for grant of rights	$ 5,000,000