Loans (Narrative) (Details)		3 Months Ended		6 Months Ended
		Jun. 30, 2016 USD ($) number	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) number	Jun. 30, 2015 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 02, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings loans		$ 299,300,000	$ 310,600,000	$ 299,300,000	$ 310,600,000
Allowance for loan losses		199,807,000	221,351,000	199,807,000	221,351,000	$ 204,034,000	$ 210,242,000		$ 228,328,000	$ 232,448,000
Average balance of impaired loans		316,045,000	348,644,000	313,222,000	347,253,000
Interest income recognized on impaired loan		$ 1,701,000	1,709,000	3,138,000	3,369,000
Forbearance agreements time period		6 months
Loans, net of unearned income	[1]	$ 18,589,337,000	16,936,772,000	18,589,337,000	16,936,772,000		17,686,502,000
Provision for loan losses		4,000,000	2,000,000	7,000,000	7,000,000
Loan loss provision on PCI loans		(400,000)	(300,000)	(300,000)	(600,000)
Allowance - purchased credit impaired loans		827,000	2,784,000	827,000	2,784,000
As Acquired | Trustatlantic Financial Corporation
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired								$ 298,100,000
As Recorded by FHN | Trustatlantic Financial Corporation
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired								$ 281,900,000
Permanent Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		$ 17,600,000	22,377,000	$ 17,600,000	22,377,000	18,754,000	18,947,000		20,186,000	19,122,000
TDR, reduction of interest rate by increment, basis points		25.00%		25.00%
TDRS Maturities		40 years
Loans, net of unearned income		$ 439,014,000	487,679,000	$ 439,014,000	487,679,000		454,123,000
Modified interest rate increase		1.00%		1.00%
Provision for loan losses		$ (1,289,000)	2,329,000	$ (2,149,000)	3,959,000
Allowance - purchased credit impaired loans		0	0	0	0
Loans Held-For-Sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings loans		73,800,000	80,800,000	$ 73,800,000	80,800,000
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage				27.00%
Consumer Real Estate Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage				25.00%
Allowance for loan losses		$ 59,081,000	85,457,000	$ 59,081,000	85,457,000	67,321,000	80,614,000		109,245,000	113,011,000
TDRS Maturities		30 years
Loans, net of unearned income	[2]	$ 4,640,779,000	4,870,271,000	4,640,779,000	4,870,271,000		4,766,518,000
Provision for loan losses		(7,740,000)	(24,736,000)	(19,842,000)	(24,689,000)
Allowance - purchased credit impaired loans		336,000	493,000	336,000	493,000
Modified Loans Classified As A TDR
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		$ 51,200,000	$ 61,000,000	$ 51,200,000	$ 61,000,000
Ratio of the allowance for loan losses to loans		17.00%	20.00%	17.00%	20.00%
Loans To Mortgage Companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage contributed in total loan		12.00%		12.00%
Percentage of commercial & industrial loan portfolio		20.00%		20.00%
Commercial loans		$ 2,227,171,000	$ 1,799,665,000	$ 2,227,171,000	$ 1,799,665,000
Loans, net of unearned income		2,227,171,000	1,799,665,000	2,227,171,000	1,799,665,000
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		111,236,000	100,242,000	111,236,000	100,242,000
Average balance of impaired loans		56,581,000	67,341,000	51,525,000	64,065,000
Interest income recognized on impaired loan		318,000	276,000	431,000	566,000
Commercial loans		$ 13,148,857,000	11,233,278,000	13,148,857,000	11,233,278,000
Time period of default probability		1 year
Allowance - purchased credit impaired loans		$ 491,000	2,291,000	491,000	2,291,000
Credit Card & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		11,890,000	13,275,000	11,890,000	13,275,000	$ 11,446,000	11,885,000		$ 13,580,000	$ 14,730,000
Loans, net of unearned income		360,687,000	345,544,000	360,687,000	345,544,000		354,536,000
Provision for loan losses		2,897,000	4,697,000	4,977,000	6,590,000
Allowance - purchased credit impaired loans		$ 0	0	$ 0	0
Credit Card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit card workout program, granted rate reduction		0.00%		0.00%
Loans, net of unearned income		$ 192,765,000	185,207,000	$ 192,765,000	185,207,000
Heloc And Real Estate Installment Classes
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR, reduction of interest rate by increment, basis points		25.00%		25.00%
Modified interest rate increase		2.00%		2.00%
Restricted And Secured Consumer Real Estate Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income		$ 43,500,000	66,400,000	$ 43,500,000	66,400,000		$ 52,800,000
Finance And Insurance Companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage contributed in total loan		12.00%		12.00%
Percentage of commercial & industrial loan portfolio		20.00%		20.00%
Commercial loans		$ 2,300,000,000		$ 2,300,000,000
Finance Insurance And Loans To Mortgage Companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of commercial & industrial loan portfolio		40.00%		40.00%
Maximum | Permanent Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified interest rate time period		5 years
Maximum | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forbearance agreements time period		12 months
Maximum | Credit Card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Payment reductions, time period		1 year
Credit card workout program, term extension		5 years
Maximum | Heloc And Real Estate Installment Classes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified interest rate time period		5 years
Minimum | Permanent Mortgage Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified interest rate		2.00%		2.00%
Modified interest rate time period		5 years
Minimum | Credit Card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Payment reductions, time period		6 months
Minimum | Heloc And Real Estate Installment Classes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified interest rate		1.00%		1.00%
Modified interest rate time period		5 years
Pass | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		12		12
Pass | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		1		1
Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		13		13
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		14		14
Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		15		15
Unlikely to be Collected Financing Receivable | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		16		16
PD Grade 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		$ 109,000	126,000	$ 109,000	126,000
Lowest expected default probability | number		1		1
PD Grade 12
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		$ 4,337,000	2,704,000	$ 4,337,000	2,704,000
PD Grade 13
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		5,669,000	$ 4,944,000	5,669,000	$ 4,944,000
PD Grade 13 | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loans		$ 500,000		$ 500,000
LGD Grade 1 | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		1		1
LGD Grade 12 | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan grades | number		12		12
Loan Reassessed | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loans		$ 1,000,000		$ 1,000,000

[1] June 30 , 2016 and 2015 and December 31, 2015 include $31.1 million, $28.3 million and $29.7 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate properties in process of f oreclosure.

[2] Balances as of June 3 0 , 2016 and 2015, and December 31, 2015, include $ 43.5 million, $ 66 . 4 million, and $ 52.8 million of restricted real estate loans, respectively. See Note 13 - Variable Interest Entities for additional information.