Collaboration Agreements (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended											3 Months Ended		12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Pfizer [Member]	Dec. 31, 2012 Pfizer [Member] Collaborative Agreement [Member]	Dec. 31, 2012 Astellas [Member] Collaborative Agreement [Member]	Dec. 31, 2012 Astellas [Member]	Dec. 31, 2012 Astellas [Member] Collaborative Agreement [Member] Minimum [Member]	Dec. 31, 2012 Astellas [Member] Collaborative Agreement [Member] Maximum [Member]	Dec. 31, 2012 Development Milestone Payments [Member]	Dec. 31, 2012 Development Milestone Payments [Member] Astellas [Member]	Dec. 31, 2008 Up-Front Cash Payment Arrangement [Member] Pfizer [Member]	Dec. 31, 2009 Up-Front Cash Payment Arrangement [Member] Astellas [Member]	Dec. 31, 2012 Up-Front Cash Payment Arrangement [Member] Astellas [Member]	Dec. 31, 2008 Development Cost-Sharing Payments [Member] Pfizer [Member] Collaborative Agreement [Member]	Dec. 31, 2012 Development Cost-Sharing Payments [Member] Astellas [Member] Collaborative Agreement [Member]	Dec. 31, 2008 Commercial Cost Sharing Payments [Member] Pfizer [Member] Collaborative Agreement [Member]	Dec. 31, 2012 Commercial Cost Sharing Payments [Member] Astellas [Member] Collaborative Agreement [Member]	Dec. 31, 2012 UCLA's [Member]	Dec. 31, 2012 Sales Milestone Payments [Member]	Dec. 31, 2012 Sales Milestone Payments [Member] Astellas [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								10.00%	20.00%
Non-refundable up-front cash payment					$ 225.0	$ 110.0						$ 225.0	$ 110.0
Eligible to receive milestone payments											335.0
Maximum eligible future sales milestone payments under collaboration arrangement																					320.0
Deferred revenue additions related to development milestones											58.0
Remaining development milestone payments the Company is eligible to receive										277.0										320.0
Percentage share of development milestone payments										10.00%	10.00%
Percentage of sales milestone payments	10.00%	10.00%	10.00%																		10.00%
Milestone and development milestone sharing payments	6.5	0.3	1.0																2.0
Development milestone payments																			4.5
Development milestone payments earned										45.0
Share percentage of developing and commercializing dimebon															60.00%		40.00%
Share percentage of developing and commercializing																50.00%		50.00%
Share percentage of developing and commercializing dimebon																33.33%		66.67%
Collaboration revenue percentage compared to U.S. XTANDI net sales	50.00%
Aggregate milestone payments received				$ 225.0			$ 168.0				$ 58.0			$ 110.0