Regulatory Capital and Restrictions - Schedule of Actual Capital Amounts and Ratios (Details) $ in Millions	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
First Horizon Corporation
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	$ 9,222	$ 7,918
Total Capital, Actual Ratio	0.1333	0.1234
Tier 1 Capital, Actual Amount	$ 8,247	$ 7,088
Tier 1 Capital, Actual Ratio	0.1192	0.1104
Common Equity Tier 1 Capital, Actual Amount	$ 7,032	$ 6,367
Common Equity Tier 1 Capital, Actual Ratio	10.17%	9.92%
Leverage, Actual Amount	$ 8,247	$ 7,088
Leverage, Actual Ratio	0.1036	0.0808
Total Capital, Capital Adequacy purposes, Amount	$ 5,533	$ 5,135
Total Capital, Capital Adequacy Purposes, Ratio	0.0800	0.0800
Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 4,150	$ 3,851
Tier 1 Capital, Capital Adequacy Purposes, Ratio	0.0600	0.0600
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 3,112	$ 2,888
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Ratio	4.50%	4.50%
Leverage, Capital Adequacy Purposes, Amount	$ 3,183	$ 3,507
Leverage, Capital Adequacy Purposes, Ratio	0.0400	0.0400
First Horizon Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	$ 8,532	$ 7,893
Total Capital, Actual Ratio	0.1241	0.1241
Tier 1 Capital, Actual Amount	$ 7,700	$ 7,133
Tier 1 Capital, Actual Ratio	0.1120	0.1122
Common Equity Tier 1 Capital, Actual Amount	$ 7,405	$ 6,838
Common Equity Tier 1 Capital, Actual Ratio	10.77%	10.75%
Leverage, Actual Amount	$ 7,700	$ 7,133
Leverage, Actual Ratio	0.0976	0.0820
Total Capital, Capital Adequacy purposes, Amount	$ 5,498	$ 5,088
Total Capital, Capital Adequacy Purposes, Ratio	0.0800	0.0800
Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 4,124	$ 3,816
Tier 1 Capital, Capital Adequacy Purposes, Ratio	0.0600	0.0600
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 3,093	$ 2,862
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Ratio	4.50%	4.50%
Leverage, Capital Adequacy Purposes, Amount	$ 3,157	$ 3,478
Leverage, Capital Adequacy Purposes, Ratio	0.0400	0.0400
Total Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 6,873	$ 6,360
Total Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.1000	0.1000
Tier 1 Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 5,498	$ 5,088
Tier 1 Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.0800	0.0800
Common Equity Tier 1 Capital. To Be Well Capitalized Under Prompt Corrective Action, Amount	$ 4,467	$ 4,134
Common Equity Tier 1 Capital. To Be Well Capitalized Under Prompt Corrective Action, Ratio	6.50%	6.50%
Leverage, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 3,946	$ 4,348
Leverage, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.0500	0.0500