Restrictions on Cash, Dividends and Lending Activities - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Average reserve balance maintained		$ 363
Short-term investments held for discharge of obligations		3,300
KeyBank (consolidated) [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Dividends paid by non banking subsidiaries		$ 1,700
KeyBank (consolidated) [Member] | Subsequent Event [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Capacity to pay dividends	$ 1,000