Consolidated Statements of Income - (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018
Huntington National Bank
Related acquisition asset losses net of asset gains	less than $1 million
Bank Mutual [Member]
Gain (Loss) on Disposition of Assets for Financial Service Operations		$ 2
ABRC [Member] | Risk Management and Shared Serivies [Member]
Gain (Loss) on Disposition of Assets for Financial Service Operations	$ 163