Variable Interest Entities - Summary of VIE Consolidated By FHN (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Assets:
Other assets	$ 4,080	$ 3,542
Liabilities:
Other liabilities	2,479	1,563
Rabbi Trusts Used For Deferred Compensation Plans
Assets:
Other assets	181	205
Liabilities:
Other liabilities	$ 150	$ 179