Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Income Tax Contingency [Line Items]
Liquidation of investment					$ (158)
Valuation allowance release						$ 0	$ (157)
Net tax benefit on intellectual property repatriation and sales						(258)	(104)
Tax expense (benefit), intra-entity transfers of assets other than inventory, amount	$ 214	$ 44	$ (43)	$ 147
Less: valuation allowance	(644)				(769)	(644)
Unrecognized tax benefits	1,532		$ 1,463		1,574	1,532	1,463	$ 1,399
Unrecognized tax benefits that would impact effective tax rate					1,500
Income tax expense (benefit), before any tax effect, related to accrued interest and penalties					74	80	$ 84
Accrued interest and penalties on unrecognized tax benefits	$ 302				376	$ 302
Undistributed earnings of foreign operations					3,700
Minimum
Income Tax Contingency [Line Items]
Tax liability increase due to proposed adjustment to taxable income					600
Maximum
Income Tax Contingency [Line Items]
Tax liability increase due to proposed adjustment to taxable income					700
Luxembourg
Income Tax Contingency [Line Items]
Valuation allowance release					(119)
Federal
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards					53
Federal \| Capital Loss Carryforward
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards					801
State
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards					4,000
State \| Capital Loss Carryforward
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards					1,400
Foreign Tax Jurisdiction
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards					1,200
Foreign Tax Jurisdiction \| Capital Loss Carryforward
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards					$ 1,200

MCKESSON CORP 10-K