Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2013
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 2 — SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (a) Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The unaudited consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for the fair statement of the Company’s financial condition, results of operations and cash flows for the periods presented, have been included. The results of operations of any interim period are not necessarily indicative of the results of operations for the full year or any other interim period. The unaudited consolidated financial statements and related disclosures have been prepared with the presumption that users of the interim unaudited consolidated financial statements have read or have access to the audited consolidated financial statements for the preceding fiscal year. Accordingly, these unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the fiscal year ended December 31, 2012 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2012, or the Annual Report, filed with the U.S. Securities and Exchange Commission, or SEC, on February 28, 2013. The consolidated balance sheet at December 31, 2012 has been derived from the audited consolidated financial statements at that date. The unaudited consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. The Company operates in one operating segment. All tabular disclosures of dollar and share amounts are presented in thousands, unless indicated otherwise. All per share amounts are presented at their actual amounts. The number of shares issuable under the Amended and Restated 2004 Equity Incentive Award Plan, or the Medivation Equity Incentive Plan, disclosed in Note 8, “Stockholder’s Equity” are presented at their actual amounts. Amounts presented herein may not calculate or sum precisely due to rounding. (b) Use of Estimates The preparation of unaudited consolidated financial statements in accordance with U.S. GAAP requires that management make estimates and assumptions in certain circumstances that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although management believes that these estimates are reasonable, actual future results could differ from those estimates. In addition, had different estimates and assumptions been used, the unaudited consolidated financial statements could have differed materially from what is presented. Estimates and assumptions used by management principally relate to: the performance periods of the Company’s deliverables under the Astellas Collaboration Agreement and its former collaboration agreement with Pfizer; collaboration revenue related to the Astellas Collaboration Agreement; services performed by third parties but not yet invoiced; the fair value and forfeiture rates of stock awards under the Medivation Equity Incentive Plan and the probability of attaining the performance objectives of performance share awards; the probability and potential magnitude of contingent liabilities; Convertible Notes, including the Company’s estimate of how the net proceeds thereof should be bifurcated between the debt component and the equity component; and deferred income taxes, income tax provisions and accruals for uncertain income tax positions. (c) Capital Structure On September 20, 2012, the Company filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation, as amended, effecting an increase in the total number of authorized shares of capital stock of the Company from 51,000,000 to 86,000,000 and an increase in the total number of authorized shares of common stock of the Company from 50,000,000 to 85,000,000. On September 21, 2012, the Company filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation, as amended, effecting (i) an increase in the total number of authorized shares of capital stock of the Company from 86,000,000 to 171,000,000, (ii) an increase in the total number of authorized shares of common stock of the Company from 85,000,000 to 170,000,000, and (iii) a two-for-one forward split of its common stock effective as of 5:00 p.m., Eastern Time, on September 21, 2012. The Company issued approximately 37.0 million shares of its common stock as a result of the two-for-one forward stock split. The par value of the Company’s common stock remained unchanged at $0.01 per share. Information regarding shares of common stock (except par value per share), additional paid-in-capital, and net (loss) income per common share for all periods presented reflects the two-for-one forward split of the Company’s common stock. The number of shares of the Company’s common stock issuable upon exercise of outstanding stock options and vesting of other stock-based awards was proportionally increased, and the exercise price per share thereof was proportionally decreased, in accordance with the terms of the Medivation Equity Incentive Plan. Following the completion of the two-for-one forward stock split, the conversion rate of the Company’s Convertible Notes was adjusted to 19.5172 shares of common stock per $1,000 principal amount of the Convertible Notes, equivalent to a conversion price of approximately $51.24 per share of common stock. (d) Significant Accounting Policies Reference is made to Note 2, “Summary of Significant Accounting Policies,” included in the notes to the Company’s audited consolidated financial statements included in its Annual Report. As of the date of the filing of this Quarterly Report on Form 10-Q, or the Quarterly Report, there were no significant changes to the significant accounting policies described in the Company’s Annual Report. (e) Recently Issued Accounting Pronouncements In February 2013, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2013-02, “Comprehensive Income (Topic 220): Reporting Amounts Reclassified Out of Accumulated Other Comprehensive Income.” This amended guidance requires companies to provide enhanced footnote disclosures to explain the effect of reclassification adjustments out of other comprehensive income, or OCI, by component and provide tabular disclosure in the footnotes showing the effect of items reclassified from accumulated OCI on the line items of net income (loss). The Company adopted this amended guidance prospectively as of January 1, 2013. The adoption of this amended guidance did not have an impact on the Company’s consolidated financial position, results of operations or cash flows. (f) Out-of-Period Adjustment In the first quarter of 2013, the Company recorded an out-of-period correcting adjustment that increased operating expenses and net loss by $3.6 million for the three months ended March 31, 2013. Management concluded that the adjustment is not material to the expected full year 2013 results or any previously reported financial statements.

NOTE 2 — SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

(a) Basis of Presentation

The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The unaudited consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for the fair statement of the Company’s financial condition, results of operations and cash flows for the periods presented, have been included. The results of operations of any interim period are not necessarily indicative of the results of operations for the full year or any other interim period.

The unaudited consolidated financial statements and related disclosures have been prepared with the presumption that users of the interim unaudited consolidated financial statements have read or have access to the audited consolidated financial statements for the preceding fiscal year. Accordingly, these unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the fiscal year ended December 31, 2012 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2012, or the Annual Report, filed with the U.S. Securities and Exchange Commission, or SEC, on February 28, 2013. The consolidated balance sheet at December 31, 2012 has been derived from the audited consolidated financial statements at that date.

The unaudited consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. The Company operates in one operating segment.

All tabular disclosures of dollar and share amounts are presented in thousands, unless indicated otherwise. All per share amounts are presented at their actual amounts. The number of shares issuable under the Amended and Restated 2004 Equity Incentive Award Plan, or the Medivation Equity Incentive Plan, disclosed in Note 8, “Stockholder’s Equity” are presented at their actual amounts. Amounts presented herein may not calculate or sum precisely due to rounding.

(b) Use of Estimates

The preparation of unaudited consolidated financial statements in accordance with U.S. GAAP requires that management make estimates and assumptions in certain circumstances that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although management believes that these estimates are reasonable, actual future results could differ from those estimates. In addition, had different estimates and assumptions been used, the unaudited consolidated financial statements could have differed materially from what is presented.

Estimates and assumptions used by management principally relate to: the performance periods of the Company’s deliverables under the Astellas Collaboration Agreement and its former collaboration agreement with Pfizer; collaboration revenue related to the Astellas Collaboration Agreement; services performed by third parties but not yet invoiced; the fair value and forfeiture rates of stock awards under the Medivation Equity Incentive Plan and the probability of attaining the performance objectives of performance share awards; the probability and potential magnitude of contingent liabilities; Convertible Notes, including the Company’s estimate of how the net proceeds thereof should be bifurcated between the debt component and the equity component; and deferred income taxes, income tax provisions and accruals for uncertain income tax positions.

(c) Capital Structure

On September 20, 2012, the Company filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation, as amended, effecting an increase in the total number of authorized shares of capital stock of the Company from 51,000,000 to 86,000,000 and an increase in the total number of authorized shares of common stock of the Company from 50,000,000 to 85,000,000.

On September 21, 2012, the Company filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation, as amended, effecting (i) an increase in the total number of authorized shares of capital stock of the Company from 86,000,000 to 171,000,000, (ii) an increase in the total number of authorized shares of common stock of the Company from 85,000,000 to 170,000,000, and (iii) a two-for-one forward split of its common stock effective as of 5:00 p.m., Eastern Time, on September 21, 2012.

The Company issued approximately 37.0 million shares of its common stock as a result of the two-for-one forward stock split. The par value of the Company’s common stock remained unchanged at $0.01 per share.

Information regarding shares of common stock (except par value per share), additional paid-in-capital, and net (loss) income per common share for all periods presented reflects the two-for-one forward split of the Company’s common stock. The number of shares of the Company’s common stock issuable upon exercise of outstanding stock options and vesting of other stock-based awards was proportionally increased, and the exercise price per share thereof was proportionally decreased, in accordance with the terms of the Medivation Equity Incentive Plan. Following the completion of the two-for-one forward stock split, the conversion rate of the Company’s Convertible Notes was adjusted to 19.5172 shares of common stock per $1,000 principal amount of the Convertible Notes, equivalent to a conversion price of approximately $51.24 per share of common stock.

(d) Significant Accounting Policies

Reference is made to Note 2, “Summary of Significant Accounting Policies,” included in the notes to the Company’s audited consolidated financial statements included in its Annual Report. As of the date of the filing of this Quarterly Report on Form 10-Q, or the Quarterly Report, there were no significant changes to the significant accounting policies described in the Company’s Annual Report.

(e) Recently Issued Accounting Pronouncements

In February 2013, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2013-02, “Comprehensive Income (Topic 220): Reporting Amounts Reclassified Out of Accumulated Other Comprehensive Income.” This amended guidance requires companies to provide enhanced footnote disclosures to explain the effect of reclassification adjustments out of other comprehensive income, or OCI, by component and provide tabular disclosure in the footnotes showing the effect of items reclassified from accumulated OCI on the line items of net income (loss). The Company adopted this amended guidance prospectively as of January 1, 2013. The adoption of this amended guidance did not have an impact on the Company’s consolidated financial position, results of operations or cash flows.

(f) Out-of-Period Adjustment

In the first quarter of 2013, the Company recorded an out-of-period correcting adjustment that increased operating expenses and net loss by $3.6 million for the three months ended March 31, 2013. Management concluded that the adjustment is not material to the expected full year 2013 results or any previously reported financial statements.