CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' DEFICIT - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury	Noncontrolling Interests
Beginning balance (in shares) at Mar. 31, 2022		275
Beginning balance (in shares) at Mar. 31, 2022						(130)
Beginning balance at Mar. 31, 2022	$ (1,792)	$ 2	$ 7,275	$ 9,030	$ (1,534)	$ (17,045)	$ 480
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employee plans, net of forfeitures (in shares)		2
Issuance of shares under employee plans, net of forfeitures	(13)	$ 1	143			$ (157)
Share-based compensation	122		122
Repurchase of common stock (in shares)						(10)
Repurchase of common stock	(3,500)		(25)			$ (3,475)
Net income	2,896			2,773			123
Other comprehensive income	679				635		44
Cash dividends declared	(222)			(222)
Payments to noncontrolling interests	(113)						(113)
Reclassification of recurring compensation to other accrued liabilities	(5)						(5)
Formation of SCRI Oncology, LLC	247		22				225
Derecognition of noncontrolling interests in McKesson Europe AG	(382)						(382)
Other	(6)		(1)	1			(6)
Ending balance (in shares) at Dec. 31, 2022		277
Ending balance at Dec. 31, 2022	(2,089)	$ 3	7,536	11,582	(899)	$ (20,677)	366
Ending balance (in shares) at Dec. 31, 2022						(140)
Beginning balance (in shares) at Sep. 30, 2022		277
Beginning balance (in shares) at Sep. 30, 2022						(135)
Beginning balance at Sep. 30, 2022	(1,249)	$ 3	7,609	10,579	(1,114)	$ (18,844)	518
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employee plans, net of forfeitures	13		16			$ (3)
Share-based compensation	36		36
Repurchase of common stock (in shares)						(5)
Repurchase of common stock	(1,976)		(146)			$ (1,830)
Net income	1,120			1,079			41
Other comprehensive income	215				215
Cash dividends declared	(77)			(77)
Payments to noncontrolling interests	(36)						(36)
Reclassification of recurring compensation to other accrued liabilities	(1)						(1)
Formation of SCRI Oncology, LLC	247		22				225
Derecognition of noncontrolling interests in McKesson Europe AG	(382)						(382)
Other	1		(1)	1			1
Ending balance (in shares) at Dec. 31, 2022		277
Ending balance at Dec. 31, 2022	$ (2,089)	$ 3	7,536	11,582	(899)	$ (20,677)	366
Ending balance (in shares) at Dec. 31, 2022						(140)
Beginning balance (in shares) at Mar. 31, 2023		277
Beginning balance (in shares) at Mar. 31, 2023	(141)					(141)
Beginning balance at Mar. 31, 2023	$ (1,490)	$ 3	7,747	12,295	(905)	$ (20,997)	367
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employee plans, net of forfeitures (in shares)		1
Issuance of shares under employee plans, net of forfeitures	(21)		75			$ (96)
Share-based compensation	136		136
Repurchase of common stock (in shares)						(6)
Repurchase of common stock	(2,381)					$ (2,381)
Net income	2,330			2,211			119
Other comprehensive income	93				93
Cash dividends declared	(240)			(240)
Payments to noncontrolling interests	(114)						(114)
Other	5		4	2			(1)
Ending balance (in shares) at Dec. 31, 2023		278
Ending balance at Dec. 31, 2023	$ (1,682)	$ 3	7,962	14,268	(812)	$ (23,474)	371
Ending balance (in shares) at Dec. 31, 2023	(147)					(147)
Beginning balance (in shares) at Sep. 30, 2023		278
Beginning balance (in shares) at Sep. 30, 2023						(145)
Beginning balance at Sep. 30, 2023	$ (1,464)	$ 3	7,899	13,761	(887)	$ (22,604)	364
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employee plans, net of forfeitures (in shares)		0
Issuance of shares under employee plans, net of forfeitures	19		21			$ (2)
Share-based compensation	45		45
Repurchase of common stock (in shares)						(2)
Repurchase of common stock	(868)					$ (868)
Net income	630			589			41
Other comprehensive income	75				75
Cash dividends declared	(83)			(83)
Payments to noncontrolling interests	(37)						(37)
Other	1		(3)	1			3
Ending balance (in shares) at Dec. 31, 2023		278
Ending balance at Dec. 31, 2023	$ (1,682)	$ 3	$ 7,962	$ 14,268	$ (812)	$ (23,474)	$ 371
Ending balance (in shares) at Dec. 31, 2023	(147)					(147)