Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,543us-gaap_ProfitLoss	$ 1,258us-gaap_ProfitLoss	$ 1,338us-gaap_ProfitLoss
Other Comprehensive Income (Loss), Net of Tax
Foreign currency translation adjustments arising during the period	(1,855)	53	(52)
Unrealized losses on cash flow hedges arising during the period	(10)	(6)	0
Unrealized losses on cash flow hedges arising during period, net of income tax benefit of nil, nil and nil	(13)	(6)	0
Retirement-related benefit plans	(124)	36	(18)
Other Comprehensive Income (Loss), Net of Tax	(1,989)	83	(70)
Comprehensive Income	(446)	1,341	1,268
Comprehensive Income Attributable to Noncontrolling Interests	212	(16)	0
Comprehensive Income Attributable to McKesson	$ (234)us-gaap_ComprehensiveIncomeNetOfTax	$ 1,325us-gaap_ComprehensiveIncomeNetOfTax	$ 1,268us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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