Term Borrowings - Schedule of Information Pertaining to Term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Term borrowings	$ 1,321	$ 1,195
Junior Subordinated Debt
Debt Instrument [Line Items]
Debt term	30 years
Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Basis spread on variable rate	0.26161%
Maturity date – May 1, 2030 - 5.75% | Senior Notes | First Horizon Bank
Debt Instrument [Line Items]
Stated interest rate	5.75%	5.75%
Term borrowings	$ 449	$ 448
0.00% on December 31, 2025 and 4.92% on December 31, 2024 | Collateralized By Loans | First Horizon Bank
Debt Instrument [Line Items]
Effective interest rate	4.28%	4.92%
Term borrowings	$ 89	$ 88
Other collateralized borrowings - SBA loans | Collateralized By Loans | First Horizon Bank
Debt Instrument [Line Items]
Debt, weighted average interest rate	6.82%	7.08%
Term borrowings	$ 12	$ 37
Other collateralized borrowings - SBA loans | Collateralized By Loans | First Horizon Bank | Minimum
Debt Instrument [Line Items]
Debt term	0 years
Other collateralized borrowings - SBA loans | Collateralized By Loans | First Horizon Bank | Maximum
Debt Instrument [Line Items]
Debt term	18 years
Maturity date – May 26, 2025 - 4.00% | Senior Notes | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	4.00%	4.00%
Term borrowings	$ 0	$ 350
Maturity date – March 7, 2031 - 5.51% | Senior Notes | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.51%	5.51%
Term borrowings	$ 497	$ 0
Maturity date – June 28, 2035 - 5.66% on December 31, 2025 and 6.30% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.66%	6.30%
Term borrowings	$ 3	$ 3
Maturity date – December 15, 2035 - 5.35% on December 31, 2025 and 5.99% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.35%	5.99%
Term borrowings	$ 19	$ 18
Maturity date – March 15, 2036 - 5.38% on December 31, 2025 and 6.02% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.38%	6.02%
Term borrowings	$ 10	$ 9
Maturity date – March 15, 2036 - 5.52% on December 31, 2025 and 6.16% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.52%	6.16%
Term borrowings	$ 12	$ 12
Maturity date – June 30, 2036 - 5.27% on December 31, 2025 and 5.91% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.27%	5.91%
Term borrowings	$ 28	$ 28
Maturity date – July 7, 2036 - 5.72% on December 31, 2025 and 6.47% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.72%	6.47%
Term borrowings	$ 19	$ 19
Maturity date – June 15, 2037 - 5.63% on December 31, 2025 and 6.27% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.63%	6.27%
Term borrowings	$ 53	$ 53
Maturity date – September 6, 2037 - 5.43% on December 31, 2025 and 6.14% on December 31, 2024 | Junior Subordinated Debt | First Horizon Corporation
Debt Instrument [Line Items]
Stated interest rate	5.43%	6.14%
Term borrowings	$ 9	$ 9
Notes payable - New Market Tax Credit investments; 17 to 34 year term, 0.93% to 4.75% on December 31, 2025; 17 to 35 year term, 0.93% to 4.75% on December 31, 2024 | Notes Payable, Other Payables | First Horizon Corporation
Debt Instrument [Line Items]
Term borrowings	$ 74	$ 74
Notes payable - New Market Tax Credit investments; 17 to 34 year term, 0.93% to 4.75% on December 31, 2025; 17 to 35 year term, 0.93% to 4.75% on December 31, 2024 | Notes Payable, Other Payables | First Horizon Corporation | Minimum
Debt Instrument [Line Items]
Debt term	17 years	17 years
Debt, weighted average interest rate	0.93%	0.93%
Notes payable - New Market Tax Credit investments; 17 to 34 year term, 0.93% to 4.75% on December 31, 2025; 17 to 35 year term, 0.93% to 4.75% on December 31, 2024 | Notes Payable, Other Payables | First Horizon Corporation | Maximum
Debt Instrument [Line Items]
Debt term	34 years	35 years
Debt, weighted average interest rate	4.75%	4.75%
Maturity date – March 31, 2031 - 9.50% | Cumulative Preferred Stock | FT Real Estate Securities Company, Inc.:
Debt Instrument [Line Items]
Stated interest rate	9.50%	9.50%
Term borrowings	$ 47	$ 47