Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands		3 Months Ended	6 Months Ended
	Jul. 31, 2015 $ / shares	Sep. 30, 2015 USD ($) shares	Jun. 30, 2015 USD ($) Segment $ / shares	Jun. 30, 2014 USD ($)	Jun. 15, 2015 shares	Dec. 31, 2014 $ / shares
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Number of operating business segment | Segment			1
Common stock, par value | $ / shares			$ 0.01			$ 0.01
Aggregate principal amount of convertible notes settled | $			$ 167,800
Repayment of convertible notes in cash | $			$ 90,994	$ 1
Scenario, Forecast [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Aggregate principal amount of convertible notes settled | $		$ 167,800
Repayment of convertible notes in cash | $		$ 167,800
Common stock, shares issued on redemption of convertible notes		1,769,609
Capital stock [Member] | Pre-Amended and Restated Certificate of Incorporation [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Shares of capital stock authorized pre-split					171,000,000
Capital stock [Member] | After-Amended and Restated Certificate of Incorporation [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Shares of capital stock authorized post-split					341,000,000
Common Stock [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Common stock split, description			On July 31, 2015, the Company announced that its Board of Directors has declared a two-for-one stock split of Medivation's common stock to be effected through a stock dividend. Shareholders of record as of August 13, 2015, will receive one additional share of Medivation common stock, par value $0.01, for each share they hold as of the record date. The share distribution is scheduled for September 15, 2015.
Common stock split, record date			Aug. 13, 2015
Common Stock [Member] | Subsequent Event [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Stock split of common stock	2
Common stock, par value | $ / shares	$ 0.01
Common Stock [Member] | Pre-Amended and Restated Certificate of Incorporation [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Shares of common stock authorized pre-split					170,000,000
Common Stock [Member] | After-Amended and Restated Certificate of Incorporation [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Shares of common stock authorized post-split					340,000,000