Pension Benefits (Schedule Of Profit Sharing Investment Plan (PSIP) Expense By Segment) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2010
Defined Benefit Plans Contribution Plan [Line Items]
Expense by segment	$ 58		$ 59		$ 1
Distribution Solutions [Member]
Defined Benefit Plans Contribution Plan [Line Items]
Expense by segment	22		23		0
Technology Solutions [Member]
Defined Benefit Plans Contribution Plan [Line Items]
Expense by segment	30		32		1
Corporate [Member]
Defined Benefit Plans Contribution Plan [Line Items]
Expense by segment	6		4		0
Cost Of Sales [Member]
Defined Benefit Plans Contribution Plan [Line Items]
Expense by segment	17	[1]	17	[1]	0	[1]
Operating Expense [Member]
Defined Benefit Plans Contribution Plan [Line Items]
Expense by segment	$ 41		$ 42		$ 1

[1] Amounts recorded to cost of sales pertain solely to our McKesson Technology Solutions segment.