Mortgage Banking Activity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Mortgage Banking [Line Items]
Net loans and leases	$ 55,872		$ 55,872		$ 57,269
Mortgage banking and title income	38	$ 4	91	$ 7
First Horizon Bank
Mortgage Banking [Line Items]
Net loans and leases	49		49
Mortgage banking and title income
Mortgage Banking [Line Items]
Mortgage banking and title income	$ 0		$ 1