CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 5,153	$ 2,310	$ 1,543
Other Comprehensive Income (Loss), Net of Tax
Foreign currency translation adjustments arising during the period	(624)	113	(1,855)
Unrealized losses on net investment hedges arising during the period	(8)	0	0
Unrealized gains (losses) on cash flow hedges arising during the period	(19)	9	(10)
Retirement-related benefit plans	(8)	50	(124)
Other Comprehensive Income (Loss), Net of Tax	(659)	172	(1,989)
Comprehensive Income (Loss)	4,494	2,482	(446)
Comprehensive (Income) Loss Attributable to Noncontrolling Interests	(4)	(72)	212
Comprehensive Income (Loss) Attributable to McKesson Corporation	$ 4,490	$ 2,410	$ (234)