Term Borrowings - Schedule of Information Pertaining To Term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 1,590	$ 1,670
Junior Subordinated Debt
Debt Instrument [Line Items]
Debt term	30 years
First Horizon Bank | Senior Notes | Maturity date – May 1, 2030 - 5.75%
Debt Instrument [Line Items]
Term borrowings	$ 447	$ 447
Stated interest rate	5.75%	5.75%
First Horizon Bank | Collateralized By Loans | 0.50% on December 31, 2021 and 0.52% on December 31, 2020 (b)
Debt Instrument [Line Items]
Term borrowings	$ 87	$ 82
Effective interest rate	0.50%	0.52%
First Horizon Bank | Collateralized By Loans | Other collateralized borrowings - SBA loans
Debt Instrument [Line Items]
Term borrowings	$ 6	$ 15
Debt, weighted average interest rate	4.10%	3.90%
First Horizon Corporation | Senior Notes | Maturity date – May 26, 2023 - 3.55%
Debt Instrument [Line Items]
Term borrowings	$ 448	$ 447
Stated interest rate	3.55%	3.55%
First Horizon Corporation | Senior Notes | Maturity date – May 26, 2025 - 4.00%
Debt Instrument [Line Items]
Term borrowings	$ 349	$ 348
Stated interest rate	4.00%	4.00%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - July 31, 2031 - 3.51% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 0	$ 7
Stated interest rate		3.51%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - November 15, 2032 - 3.50% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 9
Stated interest rate		3.50%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - March 26, 2033 - 3.40% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 5
Stated interest rate		3.40%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - June 17, 2033 - 3.40% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 9
Stated interest rate		3.40%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - March 17, 2034 - 3.02% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 6
Stated interest rate		3.02%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - September 20, 2034 - 2.25% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 8
Stated interest rate		2.25%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - June 28, 2035 - 1.88% on December 31, 2021 and 1.90% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 3	$ 3
Stated interest rate	1.88%	1.90%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - December 15, 2035 - 1.57% on December 31, 2021 and 1.59% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 18	$ 18
Stated interest rate	1.57%	1.59%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - March 15, 2036 - 1.60% on December 31, 2021 and 1.62% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 9	$ 9
Stated interest rate	1.60%	1.62%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - March 15, 2036 - 1.74% on December 31, 2021 and 1.76% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 12	$ 12
Stated interest rate	1.74%	1.76%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - June 30, 2036 - 1.54% on December 31, 2021 and 1.56% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 27	$ 27
Stated interest rate	1.54%	1.56%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - July 7, 2036 - 1.67% on December 31, 2021 and 1.79% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 18	$ 18
Stated interest rate	1.67%	1.79%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - October 7, 2036 - 1.88% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 0	$ 6
Stated interest rate		1.88%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - December 30, 2036 - 1.84% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 10
Stated interest rate		1.84%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - June 15, 2037 - 1.85% on December 31, 2021 and 1.87% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 52	$ 51
Stated interest rate	1.85%	1.87%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - September 6, 2037 - 1.61% on December 31, 2021 and 1.66% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 9	$ 9
Stated interest rate	1.61%	1.66%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - September 15, 2037 - 1.65% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	$ 0	$ 7
Stated interest rate		1.65%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - December 15, 2037 - 2.76% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 10
Stated interest rate		2.76%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - December 15, 2037 - 2.97% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 10
Stated interest rate		2.97%
First Horizon Corporation | Junior Subordinated Debt | Maturity date - June 15, 2038 - 3.72% on December 31, 2020
Debt Instrument [Line Items]
Term borrowings	0	$ 6
Stated interest rate		3.72%
First Horizon Corporation | Notes Payable, Other Payables | New Market Tax Credit Investments
Debt Instrument [Line Items]
Term borrowings	59	$ 45
FT Real Estate Securities Company, Inc. | Cumulative Preferred Stock | Maturity date – March 31, 2031 – 9.50%
Debt Instrument [Line Items]
Term borrowings	$ 46	$ 46
Stated interest rate	9.50%	9.50%
Minimum | First Horizon Bank | Collateralized By Loans | Other collateralized borrowings - SBA loans
Debt Instrument [Line Items]
Debt term	4 years
Minimum | First Horizon Corporation | Notes Payable, Other Payables | New Market Tax Credit Investments
Debt Instrument [Line Items]
Debt term	7 years
Debt, weighted average interest rate	0.93%	1.27%
Maximum | First Horizon Bank | Collateralized By Loans | Other collateralized borrowings - SBA loans
Debt Instrument [Line Items]
Debt term	25 years
Maximum | First Horizon Corporation | Notes Payable, Other Payables | New Market Tax Credit Investments
Debt Instrument [Line Items]
Debt term	35 years
Debt, weighted average interest rate	4.95%	4.95%