Restrictions on Cash, Dividends and Lending Activities - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2019	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Average reserve balance maintained		$ 377
Short-term investments held for discharge of obligations		3,800
KeyBank (consolidated) [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Dividends paid by non banking subsidiaries		$ 1,200
Capacity to pay dividends	$ 920