Stockholders' Equity (Deficit) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (1,792)	$ 175
Other comprehensive income, net of tax	636	26
Other comprehensive income attributable to McKesson	636	23
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		8
Ending balance	(1,472)	(45)
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)	64	(22)
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)	12	(5)
Total Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,534)
Other comprehensive income (loss) before reclassifications	(101)
Amounts reclassified to earnings and other	737
Other comprehensive income, net of tax	636
Less: amounts attributable to noncontrolling interests	50
Other comprehensive income attributable to McKesson	586
Ending balance	(948)
Foreign Currency Translation Adjustments, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,504)	(1,361)
Other comprehensive income (loss) before reclassifications	(176)	34
Amounts reclassified to earnings and other	730	17
Other comprehensive income, net of tax	554	51
Less: amounts attributable to noncontrolling interests	47	9
Other comprehensive income attributable to McKesson	507	42
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(158)
Ending balance	(997)	(1,477)
Unrealized Gains on Net Investment Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	10	(36)
Other comprehensive income (loss) before reclassifications	45	(27)
Amounts reclassified to earnings and other	(17)	0
Other comprehensive income, net of tax	28	(27)
Less: amounts attributable to noncontrolling interests	0	(6)
Other comprehensive income attributable to McKesson	28	(21)
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		0
Ending balance	38	(57)
Other comprehensive income (loss) before reclassifications, tax	(31)	6
Unrealized Gains on Cash Flow Hedges, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	27	13
Other comprehensive income (loss) before reclassifications	18	0
Amounts reclassified to earnings and other	0	0
Other comprehensive income, net of tax	18	0
Less: amounts attributable to noncontrolling interests	0	0
Other comprehensive income attributable to McKesson	18	0
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		0
Ending balance	45	13
Unrealized Gains (Losses) and Other Components of Benefit Plans, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(67)	(96)
Other comprehensive income (loss) before reclassifications	12	5
Amounts reclassified to earnings and other	24	(3)
Other comprehensive income, net of tax	36	2
Less: amounts attributable to noncontrolling interests	3	0
Other comprehensive income attributable to McKesson	33	2
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(12)
Ending balance	$ (34)	(106)
AOCI Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(1,480)
Other comprehensive income (loss) before reclassifications		12
Amounts reclassified to earnings and other		14
Other comprehensive income, net of tax		26
Less: amounts attributable to noncontrolling interests		3
Other comprehensive income attributable to McKesson		23
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		(170)
Ending balance		$ (1,627)