Derivatives (Narrative) (Details) (USD $)	3 Months Ended					3 Months Ended	12 Months Ended
	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Feb. 29, 2012	Dec. 31, 2011	Mar. 31, 2012 FHN [Member] Y	Dec. 31, 2011 FHN [Member] Y	Mar. 31, 2011 FHN [Member]	Mar. 31, 2012 Derivative Instruments With Accelerated Termination Provisions [Member]	Mar. 31, 2011 Derivative Instruments With Accelerated Termination Provisions [Member]	Mar. 31, 2012 Derivative Instruments With Accelerated Termination Provisions [Member] FHN [Member]	Mar. 31, 2011 Derivative Instruments With Accelerated Termination Provisions [Member] FHN [Member]	Mar. 31, 2012 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Shortcut Method [Member] FHN [Member]	Mar. 31, 2011 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Shortcut Method [Member] FHN [Member]	Mar. 31, 2012 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member]	Mar. 31, 2011 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member]	Mar. 31, 2012 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member] FHN [Member]	Mar. 31, 2011 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member] FHN [Member]	Mar. 31, 2012 Subordinated Debentures Subject To Mandatory Redemption [Member] FHN [Member]	Mar. 31, 2011 Subordinated Debentures Subject To Mandatory Redemption Amount [Member]	Mar. 31, 2012 Subordinated Debentures Subject To Mandatory Redemption Amount [Member] FHN [Member]	Mar. 31, 2012 Hedge Of Held-To-Maturity Trust Preferred Loans [Member]	Mar. 31, 2011 Hedge Of Held-To-Maturity Trust Preferred Loans [Member]	Mar. 31, 2012 Additional Derivative Agreements [Member] Derivative Instruments With Adjustable Collateral Posting Thresholds [Member]	Mar. 31, 2011 Additional Derivative Agreements [Member] Derivative Instruments With Adjustable Collateral Posting Thresholds [Member]	Mar. 31, 2012 Additional Derivative Agreements [Member] Derivative Instruments With Adjustable Collateral Posting Thresholds [Member] FHN [Member]	Mar. 31, 2011 Additional Derivative Agreements [Member] Derivative Instruments With Adjustable Collateral Posting Thresholds [Member] FHN [Member]	Mar. 31, 2011 Fixed Interest Rate Swaps To Hedge [Member] Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Shortcut Method [Member] FHN [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash receivables	$ 184,800,000		$ 134,600,000
Collateral received											278,600,000	203,600,000														278,600,000	203,600,000
Collateral cash payables	158,300,000		126,800,000
Securities posted collateral									40,800,000	30,900,000														175,300,000	134,200,000
Net fair value of derivative assets with adjustable posting thresholds											242,200,000	158,700,000														243,900,000	161,700,000
Net fair value of derivative liabilities with adjustable posting thresholds											37,500,000	32,500,000														172,900,000	136,800,000
Total trading revenues	98,600,000		83,200,000
Certain term borrowings total													904,000,000				500,000,000											904,000,000
Net fair value of interest rate derivatives hedging long-term debt using the long-haul method													92,600,000	94,200,000			25,400,000
Noncallable senior debt maturing date	December 2015
Net fair value of interest rate derivatives hedging subordinated debt using long-haul method															1,200,000	400,000		15,500,000				7,000,000	14,100,000
Other long-term debt	2,340,706,000		2,514,754,000		2,481,660,000														200,000,000	200,000,000	200,000,000
Hedged held-to-maturity trust preferred loans principal balance						196,300,000		201,600,000
Fixed rate conversion termination period, years						5	5
Estimated conversion ratio				43.00%
Additional amount deposited into escrow account by Visa			400,000,000
Cash payment to counterparty		700,000
Derivative liabilities related to sale	2,900,000
Hedged amount of foreign currency denominated loans					$ 700,000