Variable Interest Entities - Summary Of VIE Consolidated By FHN (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Other assets	$ 2,536,822	$ 2,046,338
Total assets	47,197,378	43,310,900
Liabilities:
Other liabilities	825,247	873,079
Total liabilities	42,141,798	38,234,892
Rabbi Trusts Used for Deferred Compensation Plans
Assets:
Other assets	82,904	91,873
Total assets	82,904	91,873
Liabilities:
Other liabilities	61,517	70,830
Total liabilities	$ 61,517	$ 70,830