Subsequent Events - Additional Information (Detail) $ in Millions	Oct. 13, 2017 USD ($) $ / shares	Oct. 11, 2017 USD ($)	Oct. 06, 2017 USD ($) $ / shares	Oct. 16, 2017 USD ($)	Jul. 31, 2013 USD ($)
Convertible Notes [Member]
Subsequent Event [Line Items]
Aggregate principal amount					$ 125.0
Subsequent Event [Member] | Settlement Agreement [Member]
Subsequent Event [Line Items]
Name of plaintiff			Delaware
Attorneys’ fees and expenses to the plaintiff		$ 3.8
Subsequent Event [Member] | Settlement Agreement [Member] | Convertible Notes [Member]
Subsequent Event [Line Items]
Settlement agreement, cash paid			$ 32.5
Settlement amount paid per unit to plaintiff | $ / shares			0.90
Amount held by plaintiff per unit | $ / shares			1.00
Aggregate principal amount			$ 35.8
Subsequent Event [Member] | Settlement Agreement Cash Tender Offer [Member]
Subsequent Event [Line Items]
Tender offer expiration date	Nov. 10, 2017
Subsequent Event [Member] | Settlement Agreement Cash Tender Offer [Member] | Convertible Notes [Member]
Subsequent Event [Line Items]
Remaining aggregate principal amount	$ 25.0
Offering amount of per unit debt instrument issued at discount | $ / shares	900
Principal amount of per unit debt instrument issued at discount | $ / shares	1,000
Subsequent Event [Member] | Asset Sale Agreement [Member] | Ipsen [Member]
Subsequent Event [Line Items]
Working capital adjustment receivable				$ 4.9