Business Combinations (Celesio Pro Forma) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Business Acquisition, Pro Forma Information [Line Items]
Net revenues	$ 161,483		$ 150,395
Net income attributable to McKesson	$ 1,493	[1]	$ 1,202	[1]

[1] (1)Includes $89 million of after-tax acquisition-related expenses and a $28 million after-tax charge associated with our portion of the reversal of a step-up to fair value of Celesio’s inventory at the date of acquisition. These expenses were incurred in 2014; for pro forma purposes, they are allocated to 2013.