Collaboration Agreements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended			3 Months Ended		6 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013 Collaborative agreement [Member]	Sep. 30, 2013 Collaborative agreement [Member] Astellas Pharma Inc [Member]	Dec. 31, 2009 Up-front cash payment arrangement [Member] Astellas Pharma Inc [Member]	Dec. 31, 2008 Up-front cash payment arrangement [Member] Pfizer [Member]	Jun. 30, 2013 Development milestone payments [Member] Astellas Pharma Inc [Member]	Sep. 30, 2013 Development milestone payments [Member] Astellas Pharma Inc [Member]	Sep. 30, 2013 Sales milestone payments [Member] Astellas Pharma Inc [Member]	Sep. 30, 2013 Development cost-sharing payments [Member] Collaborative agreement [Member] Astellas Pharma Inc [Member]	Dec. 31, 2008 Development cost-sharing payments [Member] Collaborative agreement [Member] Pfizer [Member]	Sep. 30, 2013 Development cost-sharing payments [Member] Collaborative agreement [Member] Pfizer [Member]	Sep. 30, 2013 Commercial cost sharing-payments [Member] Collaborative agreement [Member] Astellas Pharma Inc [Member]	Dec. 31, 2008 Commercial cost sharing-payments [Member] Collaborative agreement [Member] Medivation [Member]	Sep. 30, 2013 Commercial cost sharing-payments [Member] Collaborative agreement [Member] Medivation [Member]
Deferred Revenue Arrangement [Line Items]
Co-promotion of sales and medical affairs percentage			50.00%
Royalty received on ex-U.S. sales per collaboration arrangement				Low teens to the low twenties
Non-refundable, up-front cash payment					$ 110.0	$ 225.0
Eligible to receive milestone payments								335.0
Eligible to receive milestone payments									320.0
Milestone payments received								78.0
Remaining development milestone payments the Company is eligible to receive							257.0
Percentage share of development milestone payments								10.00%
Share percentage of developing and commercializing dimebon											60.00%	60.00%		40.00%	40.00%
Share of developing and commercializing XTANDI U.S.										50.00%			50.00%
Share of developing and commercializing XTANDI ex-U.S.										33.33%			66.67%
Collaboration revenue percentage compared to U.S. XTANDI net sales	50.00%	50.00%
Collaboration revenue attributable to ex-U.S. XTANDI sales	$ 1.6	$ 2.0