Stockholders' Deficit - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (1,240)	$ (1,472)	$ (1,490)	$ (1,792)
Other comprehensive income (loss) before reclassifications	(38)	(189)	19	(290)
Amounts reclassified to earnings and other	(1)	17	(1)	754
Other comprehensive income (loss), net of tax	(39)	(172)	18	464
Less: amounts attributable to noncontrolling interests	0	(6)	0	44
Other comprehensive income (loss) attributable to McKesson	(39)	(166)	18	420
Ending balance	(1,464)	(1,249)	(1,464)	(1,249)
Total Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(848)	(948)	(905)	(1,534)
Ending balance	(887)	(1,114)	(887)	(1,114)
Foreign Currency Translation Adjustments, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(780)	(997)	(847)	(1,504)
Other comprehensive income (loss) before reclassifications	(84)	(280)	(17)	(456)
Amounts reclassified to earnings and other	0	17	0	747
Other comprehensive income (loss), net of tax	(84)	(263)	(17)	291
Ending balance	(864)	(1,254)	(864)	(1,254)
Foreign Currency Translation Adjustments, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	(6)	0	41
Foreign Currency Translation Adjustments, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	(84)	(257)	(17)	250
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(29)	38	(14)	10
Other comprehensive income (loss) before reclassifications	20	71	5	116
Amounts reclassified to earnings and other	0	0	0	(17)
Other comprehensive income (loss), net of tax	20	71	5	99
Ending balance	(9)	109	(9)	109
Other comprehensive income (loss) before reclassification, tax	(7)	(25)	(2)	(56)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	0	0	0
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	20	71	5	99
Unrealized Gains (Losses) on Cash Flow and Other Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(29)	45	(36)	27
Other comprehensive income (loss) before reclassifications	25	18	32	36
Amounts reclassified to earnings and other	0	0	0	0
Other comprehensive income (loss), net of tax	25	18	32	36
Ending balance	(4)	63	(4)	63
Unrealized Gains (Losses) on Cash Flow and Other Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	0	0	0
Unrealized Gains (Losses) on Cash Flow and Other Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	25	18	32	36
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(10)	(34)	(8)	(67)
Other comprehensive income (loss) before reclassifications	1	2	(1)	14
Amounts reclassified to earnings and other	(1)	0	(1)	24
Other comprehensive income (loss), net of tax	0	2	(2)	38
Ending balance	(10)	(32)	(10)	(32)
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Less: amounts attributable to noncontrolling interests	0	0	0	3
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) attributable to McKesson	$ 0	$ 2	$ (2)	$ 35