Stockholders' Equity (Deficit) - Schedule of Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance		$ (1,792)	$ 175	$ 5,309
Other comprehensive income, net of tax		673	115	170
Other comprehensive income (loss) attributable to McKesson		673	112	223
Exercise of put right by noncontrolling shareholders of McKesson Europe AG			8	3
Ending balance	$ (1,490)	(1,490)	(1,792)	175
Reclassification to income statement, tax expense	6
Net Investment Hedging | Derivatives designated for hedge accounting: | Euro Denominated Notes
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Derivatives designated as net investment hedges:		7	73	(118)
Currency Swap | Derivatives designated for hedge accounting:
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Derivatives designated as net investment hedges:		28	(4)	(119)
Derivatives used in net investment hedges, gains (losses)		28	(4)	(119)
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance		(1,534)	(1,480)	(1,703)
Other comprehensive income (loss) before reclassifications		(179)	39	99
Amount reclassified to earnings and other		852	76	71
Other comprehensive income, net of tax		673	115	170
Less: amounts attributable to noncontrolling and redeemable noncontrolling interests		44	(1)	(53)
Other comprehensive income (loss) attributable to McKesson		629	116	223
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(170)
Ending balance	(905)	(905)	(1,534)	(1,480)
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance		(1,504)	(1,361)	(1,780)
Other comprehensive income (loss) before reclassifications		(329)	(51)	312
Amount reclassified to earnings and other		1,027	71	47
Other comprehensive income, net of tax		698	20	359
Less: amounts attributable to noncontrolling and redeemable noncontrolling interests		41	5	(60)
Other comprehensive income (loss) attributable to McKesson		657	15	419
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(158)
Ending balance	(847)	(847)	(1,504)	(1,361)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance		10	(36)	138
Other comprehensive income (loss) before reclassifications		112	41	(175)
Amount reclassified to earnings and other		(136)	(1)	0
Other comprehensive income, net of tax		(24)	40	(175)
Less: amounts attributable to noncontrolling and redeemable noncontrolling interests		0	(6)	(1)
Other comprehensive income (loss) attributable to McKesson		(24)	46	(174)
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		0
Ending balance	(14)	(14)	10	(36)
Unrealized gain (loss) on net investment hedges, tax		(33)	(23)	62
Unrealized Gains (Losses) on Cash Flow and Other Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance		27	13	49
Other comprehensive income (loss) before reclassifications		10	18	(36)
Amount reclassified to earnings and other		(73)	(4)	0
Other comprehensive income, net of tax		(63)	14	(36)
Less: amounts attributable to noncontrolling and redeemable noncontrolling interests		0	0	0
Other comprehensive income (loss) attributable to McKesson		(63)	14	(36)
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		0
Ending balance	(36)	(36)	27	13
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance		(67)	(96)	(110)
Other comprehensive income (loss) before reclassifications		28	31	(2)
Amount reclassified to earnings and other		34	10	24
Other comprehensive income, net of tax		62	41	22
Less: amounts attributable to noncontrolling and redeemable noncontrolling interests		3	0	8
Other comprehensive income (loss) attributable to McKesson		59	41	14
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(12)
Ending balance	$ (8)	$ (8)	$ (67)	$ (96)