Investment Securities (Schedule of FHN's Investment Securities ) (Details) (USD $)	3 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	$ 3,551,256,000	[1]	$ 3,212,355,000	[2],[3]
Securities available for sale, Gross Unrealized Gains	60,999,000	[1]	48,840,000	[2]
Securities available for sale, Gross Unrealized Losses	(35,713,000)	[1]	(32,816,000)	[2]
Securities available-for-sale	3,576,542,000	[1]	3,228,379,000	[2],[4]	3,398,457,000
Pledged available for sale securities	3,400,000,000		3,000,000,000
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	4,279,000		0		0
Securities held to maturity, Gross Unrealized Gains	1,277,000
Securities held to maturity, Gross Unrealized Losses	0
Securities held to maturity, Fair Value	5,556,000
States And Municipalities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	4,279,000
Securities held to maturity, Gross Unrealized Gains	1,277,000
Securities held to maturity, Gross Unrealized Losses	0
Securities held to maturity, Fair Value	5,556,000
FRB [Member]
Schedule of Available-for-sale Securities [Line Items]
Restricted investments	66,000,000		66,200,000
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	39,995,000		39,991,000
Securities available for sale, Gross Unrealized Gains	4,000		6,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	39,999,000		39,997,000
Government Agency Issued Mortgage-Backed Securities ("MBS") [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	724,785,000		959,851,000	[3]
Securities available for sale, Gross Unrealized Gains	39,679,000		36,205,000
Securities available for sale, Gross Unrealized Losses	(1,622,000)		(4,294,000)
Securities available-for-sale	762,842,000		991,762,000	[3]
Government Agency Issued Collateralized Mortgage Obligations ("CMO") [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	2,582,242,000		1,970,151,000
Securities available for sale, Gross Unrealized Gains	21,211,000		12,409,000
Securities available for sale, Gross Unrealized Losses	(34,065,000)		(28,522,000)
Securities available-for-sale	2,569,388,000		1,954,038,000
Other U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	1,973,000		2,687,000
Securities available for sale, Gross Unrealized Gains	88,000		167,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	2,061,000		2,854,000
States And Municipalities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	15,155,000		16,434,000
Securities available for sale, Gross Unrealized Gains	0		11,000
Securities available for sale, Gross Unrealized Losses	0		0
Securities available-for-sale	15,155,000		16,445,000
Equity and other
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	187,106,000	[5]	223,241,000	[6]
Securities available for sale, Gross Unrealized Gains	17,000	[5]	42,000	[6]
Securities available for sale, Gross Unrealized Losses	(26,000)	[5]	0	[6]
Securities available-for-sale	187,097,000	[5]	223,283,000	[6]
Schedule Of Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized cost	0
Securities held to maturity, Fair Value	$ 0

[1] Includes $3.4 billion of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes.

[2] Includes $3.0 billion of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes.

[3] Balance has been re-presented due to purchase accounting adjustments made in third quarter 2013.

[4] June 30, 2013 balance has been re-presented due to purchase accounting adjustments made in third quarter 2013.

[5] 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.

[6] Includes restricted investments in FHLB-Cincinnati stock of $128.0 million and FRB stock of $66.2 million. The remainder is money market, venture capital, and cost method investments.