Redeemable Noncontrolling Interests and Noncontrolling Interests - Schedule of Changes in Redeemable Noncontrolling Interests and Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Noncontrolling Interests
Beginning balance	$ 196
Net income attributable to noncontrolling interests	47	$ 50
Other comprehensive income (loss)	3	61
Payments to noncontrolling interests	(39)	(43)
Ending balance	484
Redeemable Noncontrolling Interests
Beginning balance	1,271
Other comprehensive income (loss)	3	61
Payments to noncontrolling interests	(39)	(43)
Reclassification of McKesson Europe redeemable noncontrolling interests	287
Ending balance	7
Noncontrolling Interests
Noncontrolling Interests
Beginning balance	196	217
Net income attributable to noncontrolling interests	39	39
Other comprehensive income (loss)	0	0
Payments to noncontrolling interests	(39)	(43)
Other	1	(6)
Ending balance	484	207
Redeemable Noncontrolling Interests
Other comprehensive income (loss)	0	0
Payments to noncontrolling interests	(39)	(43)
Reclassification of McKesson Europe redeemable noncontrolling interests	287
Other	1	(6)
Redeemable Noncontrolling Interests
Noncontrolling Interests
Other comprehensive income (loss)	3	61
Payments to noncontrolling interests	0	0
Other	3	0
Redeemable Noncontrolling Interests
Beginning balance	1,271	1,402
Net income attributable to noncontrolling interests	8	11
Other comprehensive income (loss)	3	61
Reclassification of recurring compensation to other accrued liabilities	(8)	(11)
Payments to noncontrolling interests	0	0
Exercises of Put Right	(983)	(49)
Reclassification of McKesson Europe redeemable noncontrolling interests	(287)
Other	3	0
Ending balance	$ 7	$ 1,414