Redeemable Noncontrolling Interests and Noncontrolling Interests - Schedule of Changes in Redeemable Noncontrolling Interests and Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Noncontrolling Interests
Beginning balance		$ 196		$ 196
Net income attributable to noncontrolling interests	$ 43		$ 50	90	$ 100
Other comprehensive income (loss)	0		(125)	3	(64)
Payments to noncontrolling interests	(40)		(50)	(79)	(93)
Ending balance	484			484
Redeemable Noncontrolling Interests
Beginning balance		1,271		1,271
Other comprehensive income (loss)	0		(125)	3	(64)
Payments to noncontrolling interests	(40)		(50)	(79)	(93)
Reclassification of McKesson Europe redeemable noncontrolling interests				287
Ending balance	0			0
Noncontrolling Interests
Noncontrolling Interests
Beginning balance	484	196	207	196	217
Net income attributable to noncontrolling interests	43		40	82	79
Other comprehensive income (loss)			0	0	0
Payments to noncontrolling interests	(40)		(50)	(79)	(93)
Other	(1)		3	0	(3)
Ending balance	484	484	200	484	200
Redeemable Noncontrolling Interests
Other comprehensive income (loss)			0	0	0
Reclassification of recurring compensation to other accrued liabilities	(2)			(2)
Payments to noncontrolling interests	(40)		(50)	(79)	(93)
Reclassification of McKesson Europe redeemable noncontrolling interests				287
Other	(1)		3	0	(3)
Redeemable Noncontrolling Interests
Noncontrolling Interests
Other comprehensive income (loss)			(151)	3	(90)
Payments to noncontrolling interests	0		0	0	0
Other	(7)		2	(4)	2
Redeemable Noncontrolling Interests
Beginning balance	7	1,271	1,414	1,271	1,402
Net income attributable to noncontrolling interests	0		10	8	21
Other comprehensive income (loss)			(151)	3	(90)
Reclassification of recurring compensation to other accrued liabilities	0		(10)	(8)	(21)
Payments to noncontrolling interests	0		0	0	0
Exercises of Put Right				(983)	(49)
Reclassification of McKesson Europe redeemable noncontrolling interests				(287)
Other	(7)		2	(4)	2
Ending balance	$ 0	$ 7	$ 1,265	$ 0	$ 1,265