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	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue related to U.S. XTANDI net sales	$ 575,658	$ 339,902	$ 196,208
Astellas Pharma Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
U.S. XTANDI net sales (as reported by Astellas)	1,151,317	679,805	392,415
Shared U.S. development and commercialization costs	(375,008)	(323,730)	(241,106)
Pre-tax U.S. profit	776,309	356,075	151,309
Medivation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Medivation’s share of pre-tax U.S. profit	388,154	178,037	75,655
Reimbursement of Medivation’s share of shared U.S. costs	$ 187,504	$ 161,865	$ 120,553