CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (6,174)	$ 242	$ (5,053)	$ 42
Other comprehensive income, net of tax
Foreign currency translation adjustments	107	43	181	55
Unrealized gains (losses) on cash flow hedges	(12)	8	(36)	33
Changes in retirement-related benefit plans	24	0	16	96
Other comprehensive income (loss)	119	51	161	184
Comprehensive income (loss)	(6,055)	293	(4,892)	226
Comprehensive income attributable to noncontrolling interests	(77)	(66)	(113)	(161)
Comprehensive income (loss) attributable to McKesson Corporation	$ (6,132)	$ 227	$ (5,005)	$ 65