Income Taxes	3 Months Ended
Jun. 30, 2013
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes As of June 30, 2013, we had $567 million of unrecognized tax benefits, of which $409 million would reduce income tax expense and the effective tax rate, if recognized. During the next twelve months, it is reasonably possible that audit resolutions and the expiration of statutes of limitations could potentially reduce our unrecognized tax benefits by up to $173 million. However, this amount may change because we continue to have ongoing negotiations with various taxing authorities throughout the year. We have received tax assessments of $98 million from the U.S. Internal Revenue Service (“IRS”) relating to 2003 through 2006. We disagree with a substantial portion of the tax assessments primarily relating to transfer pricing. We are pursuing administrative relief through the appeals process. We have also received assessments from the Canada Revenue Agency (“CRA”) for a total of $209 million related to transfer pricing for 2003 through 2008. Payments of most of the assessments to the CRA have been made to stop the accrual of interest. We have appealed the assessment for 2003 to the Tax Court of Canada and have filed a notice of objection for 2004 through 2008. The trial between McKesson Canada Corporation and the CRA, argued in the Tax Court of Canada, concluded in early February 2012, and we are waiting for the decision. We continue to believe in the merits of our tax positions and that we have adequately provided for any potential adverse results relating to these examinations in our financial statements. However, the final resolution of these issues could result in a significant increase or decrease to income tax expense. The IRS is currently examining our U.S. corporation income tax returns for 2007 through 2009. In nearly all jurisdictions, the tax years prior to 2003 are no longer subject to examination. We report interest and penalties on tax deficiencies as income tax expense. We recognized an income tax expense of $3 million, before any tax benefit, related to interest and penalties in our condensed consolidated statements of operations during the first quarter of 2014. At June 30, 2013, before any tax benefits, our accrued interest and penalties on unrecognized tax benefits amounted to $134 million.

Income Taxes

3 Months Ended

Jun. 30, 2013

As of June 30, 2013, we had $567 million of unrecognized tax benefits, of which $409 million would reduce income tax expense and the effective tax rate, if recognized. During the next twelve months, it is reasonably possible that audit resolutions and the expiration of statutes of limitations could potentially reduce our unrecognized tax benefits by up to $173 million. However, this amount may change because we continue to have ongoing negotiations with various taxing authorities throughout the year.

We have received tax assessments of $98 million from the U.S. Internal Revenue Service (“IRS”) relating to 2003 through 2006. We disagree with a substantial portion of the tax assessments primarily relating to transfer pricing. We are pursuing administrative relief through the appeals process. We have also received assessments from the Canada Revenue Agency (“CRA”) for a total of $209 million related to transfer pricing for 2003 through 2008. Payments of most of the assessments to the CRA have been made to stop the accrual of interest. We have appealed the assessment for 2003 to the Tax Court of Canada and have filed a notice of objection for 2004 through 2008. The trial between McKesson Canada Corporation and the CRA, argued in the Tax Court of Canada, concluded in early February 2012, and we are waiting for the decision. We continue to believe in the merits of our tax positions and that we have adequately provided for any potential adverse results relating to these examinations in our financial statements. However, the final resolution of these issues could result in a significant increase or decrease to income tax expense.

The IRS is currently examining our U.S. corporation income tax returns for 2007 through 2009. In nearly all jurisdictions, the tax years prior to 2003 are no longer subject to examination.

We report interest and penalties on tax deficiencies as income tax expense. We recognized an income tax expense of $3 million, before any tax benefit, related to interest and penalties in our condensed consolidated statements of operations during the first quarter of 2014. At June 30, 2013, before any tax benefits, our accrued interest and penalties on unrecognized tax benefits amounted to $134 million.