Variable Interest Entities (Summary Of VIE Not Consolidated By FHN) (Details) - USD ($) $ in Thousands	Jun. 30, 2018		Dec. 31, 2017		Jun. 30, 2017
Variable Interest Entity [Line Items]
Loans, net of unearned income	$ 27,701,740	[1]	$ 27,658,929	[1]	$ 19,989,319
Trading securities	1,649,470		1,416,345
Term borrowings	1,227,281		1,218,097
Securities available-for-sale			5,170,255
Low income housing partnerships
Variable Interest Entity [Line Items]
Maximum Loss Exposure	96,289		94,798
Liability Recognized	36,968		33,348
Maximum loss exposure, contractual funding commitments	37,000		33,300
Low income housing partnerships | Other Assets
Variable Interest Entity [Line Items]
Maximum loss exposure, current investments	59,300		61,500
Other tax credit investments
Variable Interest Entity [Line Items]
Maximum Loss Exposure	19,023		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	332,370		332,455
Liability Recognized	0		0
On-balance sheet trust preferred securitization
Variable Interest Entity [Line Items]
Maximum Loss Exposure	48,479		48,817
Liability Recognized	65,695		65,357
Loans, net of unearned income	112,500		112,500
Trading securities	1,700		1,700
Term borrowings	65,700		65,400
Proprietary residential mortgage securitizations
Variable Interest Entity [Line Items]
Maximum Loss Exposure	1,724		2,151
Liability Recognized	0		0
Holdings of agency mortgage-backed securities
Variable Interest Entity [Line Items]
Maximum Loss Exposure	5,092,123		5,349,287
Liability Recognized	0		0
Trading securities	500,000		500,000
Securities available-for-sale	4,600,000		4,800,000
Commercial loan troubled debt restructurings
Variable Interest Entity [Line Items]
Maximum Loss Exposure	18,612		19,411
Liability Recognized	0		0
Maximum loss exposure, contractual funding commitments	800		300
Loans, net of unearned income	17,800		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] June 30, 2018 and December 31, 2017 include $21.4 million and $22.7 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.