Collaboration Agreement - Schedule of Potential Milestone Payments in Sales (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Milestone Payment One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone Payment	$ 50
Milestone Payment Two [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone Payment	70
Milestone Payment Three [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone Payment	175
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	800
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	1,200
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	$ 1,600