Noninterest Income - Wealth Management and Trust Fees (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Income and Expenses [Abstract]
Wealth management fees	$ 20	$ 0	$ 20	$ 0
Trust fees	2	0	2	0
Wealth management and trust fees	$ 22	$ 0	$ 22	$ 0