Stockholders' Equity (Deficit) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (1,249)	$ (87)	$ (1,792)	$ (1,792)	$ 175
Other comprehensive income (loss), net of tax	215	8		679	(4)
Other comprehensive income (loss) attributable to McKesson	215	8		679	(7)
Exercise of put right by noncontrolling shareholders of McKesson Europe AG					8
Ending balance	(2,089)	(787)	(1,249)	(2,089)	(787)
Reclassified to income statement, tax	22			6
Disposed of by sale | U.K. Disposal Group (Disposal Group)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of gains from AOCI			26
Derivatives designated for hedge accounting | Net Investment Hedging | Euro Denominated Notes
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), net investment hedge, gain (loss)	(132)	23		7	34
Derivatives designated for hedge accounting | Cross-currency swaps
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), net investment hedge, gain (loss)	(7)	(2)		26	3
Total Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,114)	(1,665)	(1,534)	(1,534)	(1,480)
Other comprehensive income (loss) before reclassifications	117	9		(173)	(24)
Amounts reclassified to earnings and other	98	(1)		852	20
Other comprehensive income (loss), net of tax	215	8		679	(4)
Less: amounts attributable to noncontrolling interests	0	(2)		44	1
Other comprehensive income (loss) attributable to McKesson	215	10		635	(5)
Exercise of put right by noncontrolling shareholders of McKesson Europe AG					(170)
Ending balance	(899)	(1,655)	(1,114)	(899)	(1,655)
Foreign Currency Translation Adjustments, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,254)	(1,557)	(1,504)	(1,504)	(1,361)
Other comprehensive income (loss) before reclassifications	96	0		(360)	(47)
Amounts reclassified to earnings and other	280	0		1,027	18
Other comprehensive income (loss), net of tax	376	0		667	(29)
Less: amounts attributable to noncontrolling interests	0	(2)		41	7
Other comprehensive income (loss) attributable to McKesson	376	2		626	(36)
Exercise of put right by noncontrolling shareholders of McKesson Europe AG					(158)
Ending balance	(878)	(1,555)	(1,254)	(878)	(1,555)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	109	(25)	10	10	(36)
Other comprehensive income (loss) before reclassifications	(5)	16		111	21
Amounts reclassified to earnings and other	(119)	0		(136)	0
Other comprehensive income (loss), net of tax	(124)	16		(25)	21
Less: amounts attributable to noncontrolling interests	0	0		0	(6)
Other comprehensive income (loss) attributable to McKesson	(124)	16		(25)	27
Exercise of put right by noncontrolling shareholders of McKesson Europe AG					0
Ending balance	(15)	(9)	109	(15)	(9)
Other comprehensive income (loss) before reclassifications, tax	(15)	5		32	10
Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	63	21	27	27	13
Other comprehensive income (loss) before reclassifications	8	(6)		44	(3)
Amounts reclassified to earnings and other	(73)	0		(73)	5
Other comprehensive income (loss), net of tax	(65)	(6)		(29)	2
Less: amounts attributable to noncontrolling interests	0	0		0	0
Other comprehensive income (loss) attributable to McKesson	(65)	(6)		(29)	2
Exercise of put right by noncontrolling shareholders of McKesson Europe AG					0
Ending balance	(2)	15	63	(2)	15
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(32)	(104)	(67)	(67)	(96)
Other comprehensive income (loss) before reclassifications	18	(1)		32	5
Amounts reclassified to earnings and other	10	(1)		34	(3)
Other comprehensive income (loss), net of tax	28	(2)		66	2
Less: amounts attributable to noncontrolling interests	0	0		3	0
Other comprehensive income (loss) attributable to McKesson	28	(2)		63	2
Exercise of put right by noncontrolling shareholders of McKesson Europe AG					(12)
Ending balance	$ (4)	$ (106)	$ (32)	$ (4)	$ (106)