Mortgage Banking Activity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Mortgage Banking [Line Items]
Net loans and leases	$ 56,690			$ 56,690		$ 54,189
Mortgage banking and title income	9		$ 34	65	$ 126
Gain on sale of mortgage servicing rights				12	0
Mortgage banking and title income
Mortgage Banking [Line Items]
Mortgage banking and title income	1		$ 1	4	$ 2
Sale of mortgage servicing rights		$ 21
Gain on sale of mortgage servicing rights				12
First Horizon Bank
Mortgage Banking [Line Items]
Net loans and leases	$ 40			$ 40