Variable Interest Entities - Summary Of VIE Consolidated By FHN (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Assets
Other assets	$ 4,191	$ 4,080
Liabilities:
Other liabilities	2,161	2,479
Rabbi Trusts used for Deferred Compensation Plans
Assets
Other assets	168	181
Liabilities:
Other liabilities	$ 139	$ 150