Regulatory Capital and Restrictions - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) financialSubsidiary	Dec. 31, 2020 USD ($)	Jan. 01, 2022 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 2,891	$ 2,261
Dividend paid to parent company	$ 770	180
Number of financial subsidiaries with covered transactions | financialSubsidiary	2
First Horizon Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 2,200
Percent of capital stock and surplus threshold for credit extension to parent and certain financial subsidiaries	10.00%
Maximum amount of credit bank may extend to parent and certain financial institutions	$ 812
Covered transactions	$ 1
Percent of capital stock and surplus threshold for credit extension to affiliates	20.00%
Maximum amount of credit bank may extend to all affiliates	$ 1,600
840 Denning LLC
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Covered transactions	2
FHN Financial Securities Corp.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Covered transactions	400
First Horizon Advisors, Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Covered transactions	51
All Affiliates Member
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Covered transactions	453
Minimum | First Horizon Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Vault cash included in cash reserves	$ 464	$ 397
Subsequent Event | First Horizon Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Positive (negative) amount available for dividend payments			$ 1,100