Collaboration Agreement - Schedule of Potential Milestone Payments in Sales (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone Payment	$ 70.0	$ 50.0	$ 25.0
Milestone Payment Four [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Remaining future milestone payments eligible to receive				$ 175.0
Milestone Sales One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual global net sales of XTANDI (calendar year), as reported by Astellas				400.0
Milestone Sales Two [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual global net sales of XTANDI (calendar year), as reported by Astellas				800.0
Milestone Sales Three [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual global net sales of XTANDI (calendar year), as reported by Astellas				1,200.0
Milestone Sales Four [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual global net sales of XTANDI (calendar year), as reported by Astellas				$ 1,600.0