Significant Accounting Policies	9 Months Ended
Dec. 31, 2012
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Basis of Presentation: The condensed consolidated financial statements of McKesson Corporation (“McKesson,” the “Company,” or “we” and other similar pronouns) include the financial statements of all wholly-owned subsidiaries and majority-owned or controlled companies. We also evaluate our ownership, contractual and other interests in entities to determine if they are variable interest entities (“VIEs”), if we have a variable interest in those entities and the nature and extent of those interests. These evaluations are highly complex and involve judgment and the use of estimates and assumptions based on available historical information and management’s judgment, among other factors. Based on our evaluations, if we determine we are the primary beneficiary of such VIEs, we consolidate such entities into our financial statements. The consolidated VIEs are not material to our condensed consolidated financial statements. Intercompany transactions and balances have been eliminated. The condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and footnote disclosures normally included in the annual consolidated financial statements. To prepare the financial statements in conformity with GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of these financial statements and income and expenses during the reporting period. Actual amounts may differ from these estimated amounts. In our opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair presentation of our financial position, results of operations and cash flows for the interim periods presented. The results of operations for the quarter and nine months ended December 31, 2012 are not necessarily indicative of the results that may be expected for the entire year. These interim financial statements should be read in conjunction with the annual audited financial statements, accounting policies and financial notes included in our Annual Report on Form 10-K for the fiscal year ended March 31, 2012 previously filed with the SEC on May 2, 2012 (“2012 Annual Report”). Certain prior period amounts have been reclassified to conform to the current period presentation. The Company’s fiscal year begins on April 1 and ends on March 31. Unless otherwise noted, all references to a particular year shall mean the Company’s fiscal year. Recently Adopted Accounting Pronouncements In the first quarter of 2013, we adopted amended guidance on a retrospective basis related to the presentation of other comprehensive income. The amended guidance requires that comprehensive income, the components of net income and the components of other comprehensive income be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. We elected to report other comprehensive income and its components in a separate statement of comprehensive income. While the new guidance changed the presentation of comprehensive income, there were no changes to the components that are recognized in net income or other comprehensive income as determined under previous accounting guidance. The amended guidance did not have a material effect on our condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In December 2011 and January 2013, disclosure guidance related to the offsetting of assets and liabilities was issued. The guidance requires an entity to disclose information about offsetting assets and liabilities for derivatives, repurchase agreements and reverse purchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with specific GAAP criteria or subject to a master netting arrangement or similar agreement. The amended guidance is effective for us on a retrospective basis commencing in the first quarter of 2014. We are currently evaluating the impact of this new guidance on our condensed consolidated financial statements.

Significant Accounting Policies

Basis of Presentation: The condensed consolidated financial statements of McKesson Corporation (“McKesson,” the “Company,” or “we” and other similar pronouns) include the financial statements of all wholly-owned subsidiaries and majority-owned or controlled companies. We also evaluate our ownership, contractual and other interests in entities to determine if they are variable interest entities (“VIEs”), if we have a variable interest in those entities and the nature and extent of those interests. These evaluations are highly complex and involve judgment and the use of estimates and assumptions based on available historical information and management’s judgment, among other factors. Based on our evaluations, if we determine we are the primary beneficiary of such VIEs, we consolidate such entities into our financial statements. The consolidated VIEs are not material to our condensed consolidated financial statements. Intercompany transactions and balances have been eliminated. The condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and footnote disclosures normally included in the annual consolidated financial statements.

To prepare the financial statements in conformity with GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of these financial statements and income and expenses during the reporting period. Actual amounts may differ from these estimated amounts. In our opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair presentation of our financial position, results of operations and cash flows for the interim periods presented.

The results of operations for the quarter and nine months ended December 31, 2012 are not necessarily indicative of the results that may be expected for the entire year. These interim financial statements should be read in conjunction with the annual audited financial statements, accounting policies and financial notes included in our Annual Report on Form 10-K for the fiscal year ended March 31, 2012 previously filed with the SEC on May 2, 2012 (“2012 Annual Report”). Certain prior period amounts have been reclassified to conform to the current period presentation.

The Company’s fiscal year begins on April 1 and ends on March 31. Unless otherwise noted, all references to a particular year shall mean the Company’s fiscal year.

Recently Adopted Accounting Pronouncements

In the first quarter of 2013, we adopted amended guidance on a retrospective basis related to the presentation of other comprehensive income. The amended guidance requires that comprehensive income, the components of net income and the components of other comprehensive income be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. We elected to report other comprehensive income and its components in a separate statement of comprehensive income. While the new guidance changed the presentation of comprehensive income, there were no changes to the components that are recognized in net income or other comprehensive income as determined under previous accounting guidance. The amended guidance did not have a material effect on our condensed consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted

In December 2011 and January 2013, disclosure guidance related to the offsetting of assets and liabilities was issued. The guidance requires an entity to disclose information about offsetting assets and liabilities for derivatives, repurchase agreements and reverse purchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with specific GAAP criteria or subject to a master netting arrangement or similar agreement. The amended guidance is effective for us on a retrospective basis commencing in the first quarter of 2014. We are currently evaluating the impact of this new guidance on our condensed consolidated financial statements.