Variable Interest Entities - Summary Of VIE Consolidated By FHN (Details) - USD ($) $ in Thousands	Sep. 30, 2019		Jun. 30, 2019	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Assets:
Cash and due from banks	$ 749,719			$ 781,291
Loans, net of unearned income	31,260,833	[1]		27,535,532	[1]	$ 27,350,214
Less: Allowance for loan losses	193,149		$ 192,749	180,424		$ 185,959	$ 185,462	$ 189,555
Total net loans	31,067,684			27,355,108
Total assets	1,912,685			1,802,939
Total assets	43,717,684			40,832,258
Liabilities:
Term borrowings	1,195,096			1,170,963
Other liabilities	763,534			580,335
Total liabilities	38,721,641			36,046,878
On-Balance Sheet Consumer Loan Securitization
Assets:
Cash and due from banks	0			0
Loans, net of unearned income	12,448			16,213
Less: Allowance for loan losses	0			0
Total net loans	12,448			16,213
Total assets	24			35
Total assets	12,472			16,248
Liabilities:
Term borrowings	401			2,981
Other liabilities	0			0
Total liabilities	401			2,981
Rabbi Trusts Used for Deferred Compensation Plans
Assets:
Total assets	87,612			78,446
Total assets	87,612			78,446
Liabilities:
Other liabilities	66,051			56,700
Total liabilities	$ 66,051			$ 56,700

[1] September 30, 2019 and December 31, 2018 include $18.2 million and $28.6 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.