Collaboration Agreement - Schedule of Collaboration Revenue Related to U.S. XTANDI Net Sales (Detail) - U.S. [Member] - XTANDI [Member] - Collaborative agreement [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue related to U.S. XTANDI net sales	$ 153,793	$ 112,010
Astellas Pharma Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
U.S. XTANDI net sales (as reported by Astellas)	307,586	224,020
Shared U.S. development and commercialization costs	(130,583)	(110,313)
Pre-tax U.S. profit	177,003	113,707
Medivation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Medivation’s share of pre-tax U.S. profit	88,501	56,853
Reimbursement of Medivation’s share of shared U.S. costs	$ 65,292	$ 55,157