Restrictions on Cash, Dividends and Lending Activities (Details) $ in Millions		12 Months Ended
Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Short-term investments held for discharge of obligations	$ 2,700	$ 2,700
KeyBank (consolidated)
Restricted Cash and Cash Equivalents Items [Line Items]
Dividends paid by non banking subsidiaries		$ 675
Capacity to pay dividends	$ 2,300

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Name:	us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration