| Document and Entity Information | Mar. 09, 2020 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | MCKESSON CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0000927653 |
| Document Type | 8-K |
| Document Period End Date | Mar. 9, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-13252 |
| Entity Tax Identification Number | 94-3207296 |
| Entity Address, Address Line One | 6555 State Hwy 161 |
| Entity Address, City or Town | Irving |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 75039 |
| City Area Code | (972) |
| Local Phone Number | 446-4800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common stock, $0.01 par value |
| Trading Symbol | MCK |
| Security Exchange Name | NYSE |
| M 0.625 Notes Due 2021 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 0.625% Notes due 2021 |
| Trading Symbol | MCK21A |
| Security Exchange Name | NYSE |
| M 1.500 Notes Due 2025 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.500% Notes due 2025 |
| Trading Symbol | MCK25 |
| Security Exchange Name | NYSE |
| M 1.625 Notes Due 2026 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.625% Notes due 2026 |
| Trading Symbol | MCK26 |
| Security Exchange Name | NYSE |
| M 3.125 Notes Due 2029 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 3.125% Notes due 2029 |
| Trading Symbol | MCK29 |
| Security Exchange Name | NYSE |
