Acquisitions and Divestitures (Narrative) (Details)	9 Months Ended	10 Months Ended
	Oct. 02, 2015 USD ($) number	Oct. 17, 2014 USD ($) number	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Goodwill			$ 145,932,000	$ 145,932,000	$ 141,943,000	$ 141,943,000
Branch Acquisition | As Recorded by FHN
Business Acquisition [Line Items]
Acquisition date		Oct. 17, 2014
Number Of Bank Branches | number		13
Assets acquired		$ 437,600,000
Cash and cash equivalents		413,400,000
Premises and equipment		7,500,000
Goodwill and intangible assets		15,700,000
Deposits assumed		437,200,000
Goodwill		4,000,000
Acquisition goodwill expected to be tax deductible		$ 4,000,000
Deposit Premium		3.32%
Trustatlantic Financial Corporation | As Recorded by FHN
Business Acquisition [Line Items]
Acquisition date	Oct. 02, 2015
Business Acquisition, Name of Acquired Entity	TrustAtlantic Financial Corporation
Number Of Bank Branches | number	5
Aggregate transaction value	$ 95,000,000