Investment Securities (Schedule of FHN's Investment Securities ) (Details) (USD $)	9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	$ 3,527,756,000	[1]	$ 3,168,118,000	[2]
Securities available for sale, Gross Unrealized Gains	49,527,000	[1]	58,514,000	[2]
Securities available for sale, Gross Unrealized Losses	(42,612,000)	[1]	(39,689,000)	[2]
Securities available-for-sale	3,534,671,000	[1]	3,186,943,000	[2]	3,398,457,000
Pledged available for sale securities	3,200,000,000		2,900,000,000
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	4,286,000		0		0
Securities held to maturity, Gross Unrealized Gains	1,094,000
Securities held to maturity, Gross Unrealized Losses	0
Securities held to maturity, Fair Value	5,380,000
States And Municipalities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	4,286,000
Securities held to maturity, Gross Unrealized Gains	1,094,000
Securities held to maturity, Gross Unrealized Losses	0
Securities held to maturity, Fair Value	5,380,000
FRB [Member]
Schedule of Available-for-sale Securities [Line Items]
Restricted investments	66,000,000		66,000,000
FHLB-Cincinnati Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Restricted investments	87,900,000		128,000,000
U.S. treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	100,000		39,993,000
Securities available for sale, Gross Unrealized Gains	0		3,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	100,000		39,996,000
Government Agency Issued Mortgage-Backed Securities ("MBS") [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	685,426,000		838,077,000
Securities available for sale, Gross Unrealized Gains	33,820,000		40,944,000
Securities available for sale, Gross Unrealized Losses	(2,381,000)		(3,570,000)
Securities available-for-sale	716,865,000		875,451,000
Government Agency Issued Collateralized Mortgage Obligations ("CMO") [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	2,648,047,000		2,043,803,000
Securities available for sale, Gross Unrealized Gains	15,637,000		17,420,000
Securities available for sale, Gross Unrealized Losses	(39,999,000)		(36,102,000)
Securities available-for-sale	2,623,685,000		2,025,121,000
Other U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	1,859,000		2,381,000
Securities available for sale, Gross Unrealized Gains	70,000		147,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	1,929,000		2,528,000
States And Municipalities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	10,205,000		15,155,000
Securities available for sale, Gross Unrealized Gains	0		0
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	10,205,000		15,155,000
Equity and other
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	182,119,000	[3]	228,709,000	[4]
Securities available for sale, Gross Unrealized Gains	0	[3]	0	[4]
Securities available for sale, Gross Unrealized Losses	(232,000)	[3]	(17,000)	[4]
Securities available-for-sale	181,887,000	[3]	228,692,000	[4]
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	0
Securities held to maturity, Fair Value	$ 0

[1] Includes $3.2 billion of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes.

[2] Includes $2.9 billion of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes.

[3] Includes restricted investments in FHLB-Cincinnati stock of $87.9 million and FRB stock of $66.0 million. The remainder is money market and cost method investments.

[4] Includes restricted investments in FHLB-Cincinnati stock of $128.0 million and FRB stock of $66.0million. The remainder is money market, venture capital, and cost method investments.