| Cover Page | Jun. 30, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Jun. 30, 2020 |
| Entity Registrant Name | KeyCorp |
| Entity Incorporation, State or Country Code | OH |
| Entity File Number | 001-11302 |
| Entity Tax Identification Number | 34-6542451 |
| Entity Address, Address Line One | 127 Public Square, |
| Entity Address, City or Town | Cleveland, |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 44114-1306 |
| City Area Code | 216 |
| Local Phone Number | 689-3000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0000091576 |
| Common Stock [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Shares, $1 par value |
| Trading Symbol | KEY |
| Security Exchange Name | NYSE |
| Series E Preferred Stock [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing a 1/40th interest in a share of Fixed-to-Floating Rate Perpetual Non-Cumulative Preferred Stock, Series E) |
| Trading Symbol | KEY PrI |
| Security Exchange Name | NYSE |
| Series F Preferred Stock [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing a 1/40th interest in a share of Fixed Rate Perpetual Non-Cumulative Preferred Stock, Series F) |
| Trading Symbol | KEY PrJ |
| Security Exchange Name | NYSE |
| Series G Preferred Stock [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing a 1/40th interest in a share of Fixed Rate Perpetual Non-Cumulative Preferred Stock, Series G) |
| Trading Symbol | KEY PrK |
| Security Exchange Name | NYSE |
