Variable Interest Entities (Summary Of VIE Not Consolidated By FHN) (Details) - USD ($) $ in Thousands	Mar. 31, 2018		Dec. 31, 2017		Mar. 31, 2017
Variable Interest Entity [Line Items]
Loans, net of unearned income	$ 27,249,793	[1]	$ 27,658,929	[1]	$ 19,090,074
Trading securities	1,759,430		1,416,345
Term borrowings	1,214,967		1,218,097
Securities available-for-sale	4,826,155		5,170,255
Low Income Housing Partnerships
Variable Interest Entity [Line Items]
Maximum Loss Exposure	92,129		94,798
Liability Recognized	32,053		33,348
Maximum loss exposure, contractual funding commitments	32,100		33,300
Low Income Housing Partnerships | Other Assets
Variable Interest Entity [Line Items]
Maximum loss exposure, current investments	60,000		61,500
Other Tax Credit Investments
Variable Interest Entity [Line Items]
Maximum Loss Exposure	19,894		20,394
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	332,414		332,455
Liability Recognized	0		0
On Balance Sheet Trust Preferred Securitization
Variable Interest Entity [Line Items]
Maximum Loss Exposure	48,658		48,817
Liability Recognized	65,516		65,357
Loans, net of unearned income	112,500		112,500
Trading securities	1,700		1,700
Term borrowings	65,500		65,400
Proprietary & Agency Residential Mortgage Securitizations
Variable Interest Entity [Line Items]
Maximum Loss Exposure	1,926		2,151
Liability Recognized	0		0
Holdings Of Agency Mortgage Backed Securities
Variable Interest Entity [Line Items]
Maximum Loss Exposure	5,278,310		5,349,287
Liability Recognized	0		0
Trading securities	500,000		500,000
Securities available-for-sale	4,700,000		4,800,000
Commercial Loan Troubled Debt Restructurings
Variable Interest Entity [Line Items]
Maximum Loss Exposure	20,727		19,411
Liability Recognized	0		0
Maximum loss exposure, contractual funding commitments	1,500		300
Loans, net of unearned income	19,200		19,100
Sale Leaseback Transaction
Variable Interest Entity [Line Items]
Maximum Loss Exposure	14,827		14,827
Liability Recognized	0		0
Proprietary Trust Preferred Issuances
Variable Interest Entity [Line Items]
Maximum Loss Exposure	0		0
Liability Recognized	$ 212,378		$ 212,378

[1] March 31, 2018 and December 31, 2017 include $21.5 million and $22.7 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.