Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 29, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-11302
Entity Registrant Name	KeyCorp
Entity Incorporation, State or Country Code	OH
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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		956,370,102
Entity Central Index Key	0000091576
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false
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	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	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	Cumulative Preferred Stock, Series G)
Trading Symbol	KEY PrK
Security Exchange Name	NYSE