Commitments and Contingencies - Additional Information (Detail)	3 Months Ended			12 Months Ended
	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Commitments And Contingencies [Line Items]
Operating lease office space, in square feet | ft²				158,000
Lease expiry period				2019-12
Rent expense				$ 10,300,000	$ 8,100,000	$ 5,200,000
Percentage of sublicensing income				10.00%
Total consideration under current statement of work			$ 15,200,000
Partial payment consideration under current statement of work				$ 5,100,000
MDV9300 [Member]
Commitments And Contingencies [Line Items]
Manufacturing services and supply agreement period				3 years
Upfront and setup fees	$ 100,000	$ 200,000	$ 3,000,000
Potential payment upon completion of Manufacturing Technology Transfer				$ 5,000,000
Funding for clinical trial materials				$ 19,300,000
Funding period for clinical materials				3 years
Clinical trial materials amount paid				$ 9,000,000
Development milestone payments [Member]
Commitments And Contingencies [Line Items]
Aggregate milestone payments upon achievement of certain development and regulatory milestone events				$ 2,800,000
Percentage of sublicensing income				10.00%
Royalty percentage on sales				4.00%
Corporate Headquarters [Member]
Commitments And Contingencies [Line Items]
Operating lease office space, in square feet | ft²				143,000
Optional lease extension term				5 years