Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,258	$ 1,338	$ 1,403
Other Comprehensive Income (Loss), Net of Tax
Foreign currency translation adjustments, net of income tax expense (benefit) of $24, ($2) and $2	53	(52)	(56)
Unrealized losses on cash flow hedges, net of income tax benefit of nil, nil and nil	(6)	0	(5)
Retirement-related benefit plans, net of income tax expense (benefit) of $29, ($10) and ($9)	36	(18)	(21)
Other Comprehensive Income (Loss), Net of Tax	83	(70)	(82)
Comprehensive Income	1,341	1,268	1,321
Comprehensive Income Attributable to Noncontrolling Interests	(16)	0	0
Comprehensive Income Attributable to McKesson	1,325	1,268	1,321
Retained Earnings [Member]
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,258	$ 1,338	$ 1,403