Regulatory Capital and Restrictions - Schedule of Actual Capital Amounts and Ratios (Details) $ in Millions	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
First Horizon Corporation
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	$ 9,748	$ 10,130
Total Capital, Actual Ratio	0.1335	0.1425
Tier 1 Capital, Actual Amount	$ 8,404	$ 8,688
Tier 1 Capital, Actual Ratio	0.1151	0.1222
Common Equity Tier 1 Capital, Actual Amount	$ 7,760	$ 7,967
Common Equity Tier 1 Capital, Actual Ratio	10.63%	11.20%
Leverage, Actual Amount	$ 8,404	$ 8,688
Leverage, Actual Ratio	0.1019	0.1064
Total Capital, Capital Adequacy purposes, Amount	$ 5,843	$ 5,689
Total Capital, Capital Adequacy Purposes, Ratio	0.0800	0.0800
Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 4,382	$ 4,266
Tier 1 Capital, Capital Adequacy Purposes, Ratio	0.0600	0.0600
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 3,287	$ 3,200
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Ratio	4.50%	4.50%
Leverage, Capital Adequacy Purposes, Amount	$ 3,300	$ 3,266
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	$ 9,425	$ 9,424
Total Capital, Actual Ratio	0.1304	0.1338
Tier 1 Capital, Actual Amount	$ 8,229	$ 8,129
Tier 1 Capital, Actual Ratio	0.1138	0.1154
Common Equity Tier 1 Capital, Actual Amount	$ 7,934	$ 7,834
Common Equity Tier 1 Capital, Actual Ratio	10.98%	11.12%
Leverage, Actual Amount	$ 8,229	$ 8,129
Leverage, Actual Ratio	0.1009	0.1006
Total Capital, Capital Adequacy purposes, Amount	$ 5,783	$ 5,633
Total Capital, Capital Adequacy Purposes, Ratio	0.0800	0.0800
Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 4,337	$ 4,225
Tier 1 Capital, Capital Adequacy Purposes, Ratio	0.0600	0.0600
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Amount	$ 3,253	$ 3,169
Common Equity Tier 1 Capital, Capital Adequacy Purposes, Ratio	4.50%	4.50%
Leverage, Capital Adequacy Purposes, Amount	$ 3,262	$ 3,232
Leverage, Capital Adequacy Purposes, Ratio	0.0400	0.0400
Total Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 7,228	$ 7,042
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	$ 5,783	$ 5,633
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	$ 4,698	$ 4,577
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	$ 4,078	$ 4,040
Leverage, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.0500	0.0500