Variable Interest Entities (Summary Of VIE Not Consolidated By FHN) (Details) - USD ($) $ in Thousands	Sep. 30, 2017		Dec. 31, 2016		Sep. 30, 2016
Variable Interest Entity [Line Items]
Loans, net of unearned income	$ 20,166,091	[1]	$ 19,589,520	[1]	$ 19,555,787
Term borrowings	1,059,507		1,040,656
Trading securities	1,469,402		897,071
Securities available-for-sale	3,963,138		3,943,499
Low Income Housing Partnerships
Variable Interest Entity [Line Items]
Maximum Loss Exposure	96,007		73,582
Maximum loss exposure, contractual funding commitments	34,200		17,400
Liability Recognized	34,236		17,398
Low Income Housing Partnerships | Other Assets
Variable Interest Entity [Line Items]
Maximum loss exposure, current investments	61,800		56,200
Other Tax Credit Investments
Variable Interest Entity [Line Items]
Maximum Loss Exposure	20,444		21,898
Liability Recognized	0		0
Other Tax Credit Investments | Other Assets
Variable Interest Entity [Line Items]
Maximum loss exposure, current investments	18,000		18,000
Small Issuer Trust Preferred Holdings
Variable Interest Entity [Line Items]
Maximum Loss Exposure	332,873		332,985
Liability Recognized	0		0
On Balance Sheet Trust Preferred Securitization
Variable Interest Entity [Line Items]
Maximum Loss Exposure	48,902		49,361
Liability Recognized	65,272		64,812
Loans, net of unearned income	112,500		112,500
Term borrowings	65,300		64,800
Trading securities	1,700		1,700
Proprietary & Agency Residential Mortgage Securitizations
Variable Interest Entity [Line Items]
Maximum Loss Exposure	2,300		2,568
Liability Recognized	0		0
Holdings Of Agency Mortgage Backed Securities
Variable Interest Entity [Line Items]
Maximum Loss Exposure	4,173,080		4,163,313
Liability Recognized	0		0
Trading securities	400,000		400,000
Securities available-for-sale	3,800,000		3,800,000
Commercial Loan Troubled Debt Restructurings
Variable Interest Entity [Line Items]
Maximum Loss Exposure	21,763		42,696
Maximum loss exposure, contractual funding commitments	600		5,200
Liability Recognized	0		0
Loans, net of unearned income	21,100		37,500
Sale Leaseback Transaction
Variable Interest Entity [Line Items]
Maximum Loss Exposure	14,827		11,827
Liability Recognized	$ 0		$ 0

[1] September 30, 2017 and December 31, 2016 include $24.8 million and $28.5 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate properties in process of foreclosure.