| Cover Page | Apr. 20, 2021 | Apr. 19, 2021 | Oct. 21, 2020 |
| Entity Information [Line Items] | |||
| Document Type | 8-K | ||
| Document Period End Date | Apr. 20, 2021 | ||
| 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 | |||
| 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 | |||
| 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 | |||
| 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 | |||
| 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 |
