Investment Securities (Schedule of FHN's Investment Securities ) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	$ 3,574,144,000	[1]	$ 3,110,692,000	[2]
Securities available for sale, Gross Unrealized Gains	48,433,000	[1]	80,918,000	[2]
Securities available for sale, Gross Unrealized Losses	(51,398,000)	[1]	(1,391,000)	[2]
Securities available-for-sale	3,571,179,000	[1]	3,190,219,000	[2]	3,398,457,000
Pledged available for sale securities	3,300,000,000		2,900,000,000
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	4,274,000		0		0
Securities held to maturity, Gross Unrealized Gains	1,180,000
Securities held to maturity, Gross Unrealized Losses	0
Securities held to maturity, Fair Value	5,454,000
States And Municipalities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	4,274,000
Securities held to maturity, Gross Unrealized Gains	1,180,000
Securities held to maturity, Gross Unrealized Losses	0
Securities held to maturity, Fair Value	5,454,000
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		125,500,000
U.S. treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	39,989,000		39,992,000
Securities available for sale, Gross Unrealized Gains	1,000		2,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	39,990,000		39,994,000
Government Agency Issued Mortgage-Backed Securities ("MBS") [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	762,069,000		1,009,283,000
Securities available for sale, Gross Unrealized Gains	34,332,000		56,649,000
Securities available for sale, Gross Unrealized Losses	(3,839,000)		(381,000)
Securities available-for-sale	792,562,000		1,065,551,000
Government Agency Issued Collateralized Mortgage Obligations ("CMO") [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	2,565,310,000		1,826,314,000
Securities available for sale, Gross Unrealized Gains	13,996,000		24,049,000
Securities available for sale, Gross Unrealized Losses	(47,536,000)		(1,010,000)
Securities available-for-sale	2,531,770,000		1,849,353,000
Other U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	2,078,000		3,068,000
Securities available for sale, Gross Unrealized Gains	104,000		208,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	2,182,000		3,276,000
States And Municipalities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	15,155,000		15,255,000
Securities available for sale, Gross Unrealized Gains	0		0
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	15,155,000		15,255,000
Equity and other
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	189,543,000	[3]	216,780,000	[4]
Securities available for sale, Gross Unrealized Gains	0	[3]	10,000	[4]
Securities available for sale, Gross Unrealized Losses	(23,000)	[3]	0	[4]
Securities available-for-sale	189,520,000	[3]	216,790,000	[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 $3.3 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, venture capital, and cost method investments.

[4] Includes restricted investments in FHLB-Cincinnati stock of $125.5 million and FRB stock of $66.0 million. The remainder is money market, venture capital, and cost method investments.