Acquisitions and Divestitures (Narrative) (Details) (USD $)					5 Months Ended				10 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	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]	Oct. 17, 2014 Branch Acquisition [Member] number	Oct. 21, 2014 TrustAtlantic Financial Corporation [Member] number	Sep. 30, 2014 TrustAtlantic Financial Corporation [Member]
Business Acquisition [Line Items]
Acquisition date						Jun. 07, 2013			Oct. 21, 2014
Business Acquisition, Name of Acquired Entity					Mountain National Bank				TrustAtlantic Financial Corporation
Number Of Bank Branches					12				5
Assets acquired						$ 452,000,000
Loans acquired						249,000,000
Deposits assumed						362,000,000
Asset discount						33,000,000
Goodwill	141,943,000	141,943,000	140,479,000	134,242,000			7,700,000
Number of bank branches FTBNA agreed to purchase								13
Deposits FTBNA will assume related to pending branch acquisition								440,000,000
Deposit Premium								3.32%
Total assets	23,986,787,000	23,789,833,000	23,858,753,000							453,000,000
Total deposits	16,144,771,000	16,734,956,000	16,283,909,000							395,000,000
Aggregate transaction value										$ 80,000,000