Asset Acquisition and License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended				3 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Aug. 31, 2004	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 01, 2015	Dec. 31, 2010
Asset Acquisition [Line Items]
Restricted cash (SRX Cardio)	$ 178,000		$ 341,000		$ 178,000		$ 178,000	$ 341,000
Net income attributable to Non Controlling interest (SRX Cardio)					(923,000)	$ 1,853,000	930,000
Research and development expense							246,854,000	$ 200,376,000	$ 123,639,000
Millennium
Asset Acquisition [Line Items]
Notice period for agreement termination				30 days
Millennium | United States
Asset Acquisition [Line Items]
Milestone payable for approval event	5,000,000				5,000,000		5,000,000
Additional milestone payable for other indications approved	23,000,000				23,000,000		23,000,000
Millennium | Europe
Asset Acquisition [Line Items]
Milestone payable for approval event	5,000,000				5,000,000		5,000,000
Additional milestone payable for other indications approved	23,000,000				23,000,000		$ 23,000,000
Millennium | Research and Development Expense
Asset Acquisition [Line Items]
Milestone payment	2,000,000
Astellas Pharma Inc
Asset Acquisition [Line Items]
Percentage required to pay for any payment received under collaboration excluding royalties											20.00%
Research and development expense	1,800,000
Maximum | Astellas Pharma Inc
Asset Acquisition [Line Items]
Milestone payable on occurrence of specified events											$ 71,500,000
SRX Cardio
Asset Acquisition [Line Items]
Variable interest entity, Terms of arrangements							Accordingly, SRX Cardio is subject to consolidation and we have consolidated the financial statements of SRX Cardio since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; and (b) allocating income or loss attributable to the noncontrolling interest in SRX Cardio to net income or loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet.
Variable interest entity, Upfront payment		$ 2,200,000	$ 500,000
Fair value of indefinite lived intangible assets										$ 3,200,000
Noncontrolling interest in variable Interest entity										$ 2,900,000
Restricted cash (SRX Cardio)	$ 178,000				$ 178,000		$ 178,000
Decrease in fair value of contingent future payments							$ 870,000
SRX Cardio | License Agreement
Asset Acquisition [Line Items]
Notice period for agreement termination		90 days
SRX Cardio | Maximum | License Agreement
Asset Acquisition [Line Items]
Research and development milestone payment obligation		$ 152,500,000				$ 152,500,000
Percentage of royalties on worldwide net sales, obligated to pay		6.00%
SRX Cardio | Minimum | License Agreement
Asset Acquisition [Line Items]
Percentage of royalties on worldwide net sales, obligated to pay		2.00%