Business Combinations (Acquisition Expenses And Related Adjustments By Segment) (Details) (USD $)	2 Months Ended	12 Months Ended
Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Acquisition Expenses and Related Adjustments	$ 218,000,000	$ 218,000,000	$ 1,000,000	$ 26,000,000
Integration Related Costs	89,000,000		0	0
Gain on business combination		0	81,000,000	0
Operating Expense [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Transaction closing expenses		39,000,000	16,000,000	3,000,000
Total Acquisition and Integration Related Costs		155,000,000	(10,000,000)	26,000,000
Restructuring, severance and relocation		43,000,000	30,000,000	3,000,000
Integration Related Costs		73,000,000	25,000,000	20,000,000
Gain on business combination		0	81,000,000	0
Distribution Solutions [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Acquisition and Integration Related Costs		119,000,000	47,000,000	24,000,000
Technology Solutions [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Acquisition and Integration Related Costs		15,000,000	7,000,000	1,000,000
Corporate [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Acquisition and Integration Related Costs		21,000,000	(64,000,000)	1,000,000
Corporate - Other Income		(14,000,000)	0	0
Corporate - Interest Expense		46,000,000	11,000,000	0
Corporate [Member] \| PSS World Medical [Member] \| Bridge Loan [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Corporate - Interest Expense			11,000,000
Operating Segments [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total Acquisition and Integration Related Costs		155,000,000	(10,000,000)	26,000,000
Cost of Sales [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Integration Related Costs		$ 3,000,000	$ 0	$ 0

Business combination cost reimbursement expense from former shareholders

No definition available.

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Namespace Prefix:	mck_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Restructuring, Serverance and Relocation Costs Related to Acquisitions

+ References

No definition available.

+ Details

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Namespace Prefix:	mck_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Transaction and integration expenses that are directly related to acquisitions by the Company. Examples include transaction closing costs, professional service fees, restructuring or severance charges, retention payments, employee relocation expenses, facility or other exit-related expenses, recoveries of acquisition-related expenses or post-closing expenses, and gains or losses on business combinations, excluding any adjustments to non-operating income and expenses.

+ References

No definition available.

+ Details

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Namespace Prefix:	mck_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Period Type:	instant

- Details

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Balance Type:	na
Period Type:	duration

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e1043-128460

+ Details

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- Definition

Costs incurred to effect a business combination which have been expensed during the period. Such costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)(2)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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- Definition

Represents the charge against earnings during the period for commitment fees and debt issuance expenses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 5

+ Details

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