CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 297	$ 5,153	$ 2,310
Other Comprehensive Income (Loss), Net of Tax
Foreign currency translation adjustments arising during the period	624	(632)	113
Unrealized gains (losses) on cash flow hedges arising during the period	(30)	(19)	9
Retirement-related benefit plans	15	(8)	50
Other Comprehensive Income (Loss), Net of Tax	609	(659)	172
Comprehensive Income	906	4,494	2,482
Comprehensive (Income) Attributable to Noncontrolling Interests	(415)	(4)	(72)
Comprehensive Income Attributable to McKesson Corporation	$ 491	$ 4,490	$ 2,410