Acquisitions and Divestitures (Narrative) (Details) (USD $)	9 Months Ended					5 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Jun. 07, 2013 Mountain National Bank [Member] number	Jun. 07, 2013 Mountain National Bank [Member] Acquired From FDIC [Member]	Jun. 07, 2013 Mountain National Bank [Member] As Recorded by FHN [Member]
Business Acquisition [Line Items]
Acquisition date						Jun. 07, 2013
Business Acquisition, Name of Acquired Entity	Mountain National Bank
Number Of Bank Branches					12
Assets acquired						$ 451,577,000	$ 416,045,000
Loans acquired						249,001,000	215,907,000
Deposits assumed						362,098,000	362,098,000
Asset discount						33,000,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Reasons	FHN continues to analyze the estimates of the fair value of the assets acquired and liabilities assumed, and as such the amounts recorded are provisional. FHN believes that information provides a reasonable basis for estimating fair values. FHN expects to substantially complete the purchase price allocation by the end of 2013; however, the fair value estimates are subject to refinement for up to one year after the closing date of the acquisition as additional information relative to closing date fair values becomes available. In addition, the tax treatment is complex and subject to interpretations that may result in future adjustments of deferred taxes as of the acquisition date.
Goodwill	140,479,000	134,242,000	134,242,000	133,659,000			6,237,000
Acquisition goodwill expected to be tax deductible					$ 3,500,000