Commitments and Contingent Liabilities	6 Months Ended
Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Commitments and Contingent Liabilities In addition to commitments and obligations in the ordinary course of business, we are subject to various claims, other pending and potential legal actions for damages, investigations relating to governmental laws and regulations and other matters arising out of the normal conduct of our business. As described below, many of these proceedings are at preliminary stages and many seek an indeterminate amount of damages. When a loss is considered probable and reasonably estimable, we record a liability in the amount of our best estimate for the ultimate loss. However, the likelihood of a loss with respect to a particular contingency is often difficult to predict and determining a meaningful estimate of the loss or a range of loss may not be practicable based on the information available and the potential effect of future events and decisions by third parties that will determine the ultimate resolution of the contingency. Moreover, it is not uncommon for such matters to be resolved over many years, during which time relevant developments and new information must be reevaluated at least quarterly to determine both the likelihood of potential loss and whether it is possible to reasonably estimate a range of possible loss. When a loss is probable but a reasonable estimate cannot be made, disclosure of the proceeding is provided. Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. We review all contingencies at least quarterly to determine whether the likelihood of loss has changed and to assess whether a reasonable estimate of the loss or range of loss can be made. As discussed above, development of a meaningful estimate of loss or a range of potential loss is complex when the outcome is directly dependent on negotiations with or decisions by third parties, such as regulatory agencies, the court system and other interested parties. Such factors bear directly on whether it is possible to reasonably estimate a range of potential loss and boundaries of high and low estimates. Significant developments in previously reported proceedings and in other litigation and claims, since the filing of our 2014 Annual Report are set out below. Unless otherwise stated, we are currently unable to estimate a range of reasonably possible losses for the unresolved proceedings described below. Should any one or a combination of more than one of these proceedings be successful, or should we determine to settle any or a combination of these matters, we may be required to pay substantial sums, become subject to the entry of an injunction or be forced to change the manner in which we operate our business, which could have a material adverse impact on our financial position or results of operations. Litigation, Government Subpoenas and Investigations As previously disclosed, on May 21, 2014, four hedge funds managed by Magnetar Capital filed a complaint against Dragonfly GmbH & Co KGaA (“Dragonfly”), a wholly-owned subsidiary of the Company, in a German court in Frankfurt, Germany, alleging that Dragonfly violated German takeover law in connection with the Company’s acquisition of Celesio by paying more to some holders of Celesio’s convertible bonds than it paid to the shareholders of Celesio’s stock, Magnetar Capital Master Fund Ltd. et al. v. Dragonfly GmbH & Co KGaA, (No. 3-05 O 44/14). Dragonfly filed its Statement of Defense on August 5, 2014, and Magnetar filed a reply on September 18, 2014. The initial oral hearing in the matter is set for November 18, 2014. On August 1, 2014, U.S. Oncology Specialty, LP (“USOS”), an indirect wholly-owned subsidiary of the Company, filed a motion to dismiss the previously reported qui tam complaint filed in the United States District Court for the Eastern District of New York by a relator, purportedly on behalf of the United States and twelve states, against USOS and fifteen oncology practices, United States ex rel. Hanks v. U.S. Oncology Specialty, LP, et al., (CV 04-3983 (SJ)). The United States chose not to intervene. The Court has not yet ruled on USOS’s motion to dismiss. On July 25, 2012, a qui tam complaint was filed under seal in the United States District Court for the Middle District of Tennessee against the Company by a relator on behalf of the United States, United States ex rel. Terrell W. Fox v. McKesson Corporation, et al., Civil Action No. 3:12-cv-766. In August 2014, McKesson, the United States, and the relator reached a settlement of the litigation, resolving the previously reported investigation regarding the distribution procedures with respect to the Vaccine for Children’s Program administered by the Centers for Disease Control and Prevention. On August 8, 2014, the United States intervened for purposes of settlement and dismissal of the action. On August 11, 2014, the court entered orders unsealing and dismissing the action. From time to time, the Company receives subpoenas or requests for information from various government agencies. The Company generally responds to such subpoenas and requests in a cooperative, thorough and timely manner. These responses sometimes require time and effort and can result in considerable costs being incurred by the Company. Such subpoenas and requests also can lead to the assertion of claims or the commencement of civil or criminal legal proceedings against the Company and other members of the healthcare industry, as well as to substantial settlements. Examples of such subpoenas and investigations are included in the Company’s 2014 Annual Report on Form 10-K, and include subpoenas from the U.S. Drug Enforcement Administration to certain of the Company’s pharmaceutical distribution facilities seeking information and records about the Company’s distribution of certain controlled substances. The Company continues to receive and respond to these requests. In addition, as previously reported, the Company was informed in the third quarter of 2014 of an investigation by the United States Department of Justice through the United States Attorney’s Office for the Northern District of West Virginia of potential claims under the Comprehensive Drug Abuse Prevention and Control Act relating to the Company’s pharmaceutical distribution of certain controlled substances by its Landover, Maryland distribution center, which closed in 2012. The Company has also received in the second quarter of 2015 a letter from the United States Attorney’s Office for the District of Colorado advising of an investigation and similar potential claims relating to the Company’s distribution of certain controlled substances by its Aurora, Colorado distribution center. The Department of Justice and other United States Attorney’s offices are also involved in the distribution center investigations. Average Wholesale Price Litigation and Claims The Company has a reserve relating to Average Wholesale Price (“AWP”) public entity claims. AWP involves a benchmark which is utilized by some public and private payers to calculate a portion of the amount that pharmacies and other providers are reimbursed for dispensing certain covered prescription drugs. Our AWP litigation reserve is reviewed at least quarterly and whenever events or circumstances indicate changes, including consideration of the pace and progress of discussions relating to potentially resolving other public entity claims. During the second quarter and first six months of 2014, we recorded a pre-tax charge of $35 million and $50 million relating to these claims within our Distribution Solutions segment. At September 30, 2014 and March 31, 2014, the AWP litigation reserve was $5 million, which was included in other current liabilities in the condensed consolidated balance sheets.

Commitments and Contingent Liabilities

In addition to commitments and obligations in the ordinary course of business, we are subject to various claims, other pending and potential legal actions for damages, investigations relating to governmental laws and regulations and other matters arising out of the normal conduct of our business. As described below, many of these proceedings are at preliminary stages and many seek an indeterminate amount of damages.

When a loss is considered probable and reasonably estimable, we record a liability in the amount of our best estimate for the ultimate loss. However, the likelihood of a loss with respect to a particular contingency is often difficult to predict and determining a meaningful estimate of the loss or a range of loss may not be practicable based on the information available and the potential effect of future events and decisions by third parties that will determine the ultimate resolution of the contingency. Moreover, it is not uncommon for such matters to be resolved over many years, during which time relevant developments and new information must be reevaluated at least quarterly to determine both the likelihood of potential loss and whether it is possible to reasonably estimate a range of possible loss. When a loss is probable but a reasonable estimate cannot be made, disclosure of the proceeding is provided.

Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. We review all contingencies at least quarterly to determine whether the likelihood of loss has changed and to assess whether a reasonable estimate of the loss or range of loss can be made. As discussed above, development of a meaningful estimate of loss or a range of potential loss is complex when the outcome is directly dependent on negotiations with or decisions by third parties, such as regulatory agencies, the court system and other interested parties. Such factors bear directly on whether it is possible to reasonably estimate a range of potential loss and boundaries of high and low estimates.

Significant developments in previously reported proceedings and in other litigation and claims, since the filing of our 2014 Annual Report are set out below. Unless otherwise stated, we are currently unable to estimate a range of reasonably possible losses for the unresolved proceedings described below. Should any one or a combination of more than one of these proceedings be successful, or should we determine to settle any or a combination of these matters, we may be required to pay substantial sums, become subject to the entry of an injunction or be forced to change the manner in which we operate our business, which could have a material adverse impact on our financial position or results of operations.

Litigation, Government Subpoenas and Investigations

As previously disclosed, on May 21, 2014, four hedge funds managed by Magnetar Capital filed a complaint against Dragonfly GmbH & Co KGaA (“Dragonfly”), a wholly-owned subsidiary of the Company, in a German court in Frankfurt, Germany, alleging that Dragonfly violated German takeover law in connection with the Company’s acquisition of Celesio by paying more to some holders of Celesio’s convertible bonds than it paid to the shareholders of Celesio’s stock, Magnetar Capital Master Fund Ltd. et al. v. Dragonfly GmbH & Co KGaA, (No. 3-05 O 44/14). Dragonfly filed its Statement of Defense on August 5, 2014, and Magnetar filed a reply on September 18, 2014. The initial oral hearing in the matter is set for November 18, 2014.

On August 1, 2014, U.S. Oncology Specialty, LP (“USOS”), an indirect wholly-owned subsidiary of the Company, filed a motion to dismiss the previously reported qui tam complaint filed in the United States District Court for the Eastern District of New York by a relator, purportedly on behalf of the United States and twelve states, against USOS and fifteen oncology practices, United States ex rel. Hanks v. U.S. Oncology Specialty, LP, et al., (CV 04-3983 (SJ)). The United States chose not to intervene. The Court has not yet ruled on USOS’s motion to dismiss.

On July 25, 2012, a qui tam complaint was filed under seal in the United States District Court for the Middle District of Tennessee against the Company by a relator on behalf of the United States, United States ex rel. Terrell W. Fox v. McKesson Corporation, et al., Civil Action No. 3:12-cv-766. In August 2014, McKesson, the United States, and the relator reached a settlement of the litigation, resolving the previously reported investigation regarding the distribution procedures with respect to the Vaccine for Children’s Program administered by the Centers for Disease Control and Prevention. On August 8, 2014, the United States intervened for purposes of settlement and dismissal of the action. On August 11, 2014, the court entered orders unsealing and dismissing the action.

From time to time, the Company receives subpoenas or requests for information from various government agencies. The Company generally responds to such subpoenas and requests in a cooperative, thorough and timely manner. These responses sometimes require time and effort and can result in considerable costs being incurred by the Company. Such subpoenas and requests also can lead to the assertion of claims or the commencement of civil or criminal legal proceedings against the Company and other members of the healthcare industry, as well as to substantial settlements. Examples of such subpoenas and investigations are included in the Company’s 2014 Annual Report on Form 10-K, and include subpoenas from the U.S. Drug Enforcement Administration to certain of the Company’s pharmaceutical distribution facilities seeking information and records about the Company’s distribution of certain controlled substances. The Company continues to receive and respond to these requests. In addition, as previously reported, the Company was informed in the third quarter of 2014 of an investigation by the United States Department of Justice through the United States Attorney’s Office for the Northern District of West Virginia of potential claims under the Comprehensive Drug Abuse Prevention and Control Act relating to the Company’s pharmaceutical distribution of certain controlled substances by its Landover, Maryland distribution center, which closed in 2012. The Company has also received in the second quarter of 2015 a letter from the United States Attorney’s Office for the District of Colorado advising of an investigation and similar potential claims relating to the Company’s distribution of certain controlled substances by its Aurora, Colorado distribution center. The Department of Justice and other United States Attorney’s offices are also involved in the distribution center investigations.

Average Wholesale Price Litigation and Claims

The Company has a reserve relating to Average Wholesale Price (“AWP”) public entity claims. AWP involves a benchmark which is utilized by some public and private payers to calculate a portion of the amount that pharmacies and other providers are reimbursed for dispensing certain covered prescription drugs. Our AWP litigation reserve is reviewed at least quarterly and whenever events or circumstances indicate changes, including consideration of the pace and progress of discussions relating to potentially resolving other public entity claims. During the second quarter and first six months of 2014, we recorded a pre-tax charge of $35 million and $50 million relating to these claims within our Distribution Solutions segment. At September 30, 2014 and March 31, 2014, the AWP litigation reserve was $5 million, which was included in other current liabilities in the condensed consolidated balance sheets.