Investment Securities (Schedule Of FHN's Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	$ 3,969,657	$ 3,971,435
Securities available for sale, Gross Unrealized Gains		19,869
Securities available for sale, Gross Unrealized Losses		(47,805)
Securities available-for-sale	3,963,138	3,943,499
Pledged available for sale securities	3,300,000	3,300,000
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, Amortized cost	10,000	14,347
Securities held to maturity, Gross Unrealized Gains	0	426
Securities held to maturity, Gross Unrealized Losses	(15)	0
Held-to-maturity Securities, Fair Value	9,985	14,773
FRB
Schedule of Available-for-sale Securities [Line Items]
Restricted investments	68,600	68,600
FHLB-Cincinnati Stock
Schedule of Available-for-sale Securities [Line Items]
Restricted investments	87,900	87,900
SBA - Interest Only Strips
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale	3,123
States And Municipalities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, Amortized cost		4,347
Securities held to maturity, Gross Unrealized Gains		393
Securities held to maturity, Gross Unrealized Losses		0
Held-to-maturity Securities, Fair Value		4,740
Corporate Bonds
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, Amortized cost	10,000	10,000
Securities held to maturity, Gross Unrealized Gains	0	33
Securities held to maturity, Gross Unrealized Losses	(15)	0
Held-to-maturity Securities, Fair Value	9,985	10,033
U.S. treasuries
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	100	100
Securities available for sale, Gross Unrealized Gains	0	0
Securities available for sale, Gross Unrealized Losses	0	0
Securities available-for-sale	100	100
Government Agency Issued Mortgage-Backed Securities ("MBS")
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	2,081,677	2,217,593
Securities available for sale, Gross Unrealized Gains	15,993	14,960
Securities available for sale, Gross Unrealized Losses	(10,165)	(23,866)
Securities available-for-sale	2,087,505	2,208,687
Government Agency Issued Collateralized Mortgage Obligations ("CMO")
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	1,701,467	1,566,986
Securities available for sale, Gross Unrealized Gains	4,295	4,909
Securities available for sale, Gross Unrealized Losses	(19,767)	(23,937)
Securities available-for-sale	1,685,995	1,547,958
Equity and other
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	186,413	186,756
Securities available for sale, Gross Unrealized Gains	2	0
Securities available for sale, Gross Unrealized Losses	0	(2)
Securities available-for-sale	186,415	$ 186,754
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, Amortized cost	0
Held-to-maturity Securities, Fair Value	0
Securities available-for-sale, excluding interest only strip:
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, Amortized Cost	3,969,657
Securities available for sale, Gross Unrealized Gains	20,290
Securities available for sale, Gross Unrealized Losses	(29,932)
Securities available-for-sale	$ 3,960,015

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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