Stockholders' Equity (Deficit) - Schedule of Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance	$ (1,490)	$ (1,792)	$ 175
Other comprehensive income, net of tax	24	673	115
Other comprehensive income (loss) attributable to McKesson	24	673	112
Exercise of put right by noncontrolling shareholders of McKesson Europe AG			8
Ending balance	(1,599)	(1,490)	(1,792)
Reclassification to income statement, tax expense		6	6
Net Investment Hedging | Derivatives designated for hedge accounting: | Cross-currency swaps
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss), net investment hedge, gain (loss)	3	28	(4)
Net Investment Hedging | Derivatives designated for hedge accounting: | Euro Denominated Notes
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss), net investment hedge, gain (loss)	0	7	73
Cash Flow Hedging | Derivatives designated for hedge accounting: | Fixed interest rate swaps
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax	14	(30)	39
Cash Flow Hedging | Derivatives designated for hedge accounting: | Cross-currency swaps
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax	39	(54)	(18)
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance	(905)	(1,534)	(1,480)
Other comprehensive income (loss) before reclassifications	26	(179)	39
Amount reclassified to earnings and other	(2)	852	76
Other comprehensive income, net of tax	24	673	115
Less: amounts attributable to noncontrolling interests	0	44	(1)
Other comprehensive income (loss) attributable to McKesson	24	629	116
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(170)
Ending balance	(881)	(905)	(1,534)
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance	(847)	(1,504)	(1,361)
Other comprehensive income (loss) before reclassifications	(9)	(329)	(51)
Amount reclassified to earnings and other	0	1,027	71
Other comprehensive income, net of tax	(9)	698	20
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(158)
Ending balance	(856)	(847)	(1,504)
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	(9)	657	15
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	41	5
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Beginning balance	(14)	10	(36)
Other comprehensive income (loss) before reclassifications	2	112	41
Amount reclassified to earnings and other	0	(136)	(1)
Other comprehensive income, net of tax	2	(24)	40
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		0
Ending balance	(12)	(14)	10
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax | Net Investment Hedging
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassification, tax	(1)	(33)	(23)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax | Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassification, tax	14	(21)	7
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	0	(6)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	2	(24)	46
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	(36)	27	13
Other comprehensive income (loss) before reclassifications	39	10	18
Amount reclassified to earnings and other	0	(73)	(4)
Other comprehensive income, net of tax	39	(63)	14
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		0
Ending balance	3	(36)	27
Unrealized Gains (Losses) on Cash Flow and other Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	0	0
Unrealized Gains (Losses) on Cash Flow and other Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	39	(63)	14
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	(8)	(67)	(96)
Other comprehensive income (loss) before reclassifications	(6)	28	31
Amount reclassified to earnings and other	(2)	34	10
Other comprehensive income, net of tax	(8)	62	41
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(12)
Ending balance	(16)	(8)	(67)
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	3	0
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
Accumulated Other Comprehensive Income (Loss), Change, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	$ (8)	$ 59	$ 41