Noncontrolling Interests (Changes in Noncontrolling Interests) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Dec. 31, 2014
Noncontrolling Interest [Line Items]
Noncontrolling interests, beginning balance	$ 1,796us-gaap_MinorityInterest
Net income attributable to noncontrolling interests	5
Other comprehensive income	(164)
NCI change from shares acquired	(60)
Dividends paid to noncontrolling interest shareholders	(16)
Reclassification from equity to temporary equity	(1,500)mck_ReclassificationfromPermanentEquity
Reclassification from equity to liability	0
Other	11mck_NoncontrollingInterestsChangesOther
Noncontrolling interests, ending balance	72us-gaap_MinorityInterest
Celesio [Member]
Noncontrolling Interest [Line Items]
Other comprehensive income	(138)
NCI change from shares acquired	(35)
Dividends paid to noncontrolling interest shareholders	$ (16)

Net Income (Loss) Attributable to Noncontrolling Interests Excluding Redeemable Noncontrolling Interests

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- Definition

Noncontrolling Interests, Changes, Other

+ References

No definition available.

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- Definition

Reclassification from an equity account to liabilities

+ References

No definition available.

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- Definition

Reclassifications out of permanent equity

+ References

No definition available.

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- Definition

Represents the purchase by the parent of an additional equity interest in a subsidiary during the period, thereby effecting a change in total (consolidated) equity attributable to the parent. The purchase of the additional equity interest represented by this element increases the parent's controlling interest in the subsidiary.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

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-Name Accounting Standards Codification

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-Section S99

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-URI http://asc.fasb.org/extlink&oid=35736750&loc=SL4591554-111686

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.31)

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-Number 210

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-Article 5

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 20

-Article 7

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- Definition

Amount after tax of other comprehensive income (loss) attributable to noncontrolling interests.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Topic 810

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-Subparagraph (c)(3)

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- Definition

Amount of cash outflow in the form of ordinary dividends provided by the non-wholly owned subsidiary to noncontrolling interests.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a)

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