Acquisitions and Divestitures (Narrative) (Details)	10 Months Ended
	Oct. 21, 2014 number	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 17, 2014 USD ($) number	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 145,932,000	$ 145,932,000		$ 141,943,000	$ 141,943,000
Branch Acquisition
Business Acquisition [Line Items]
Number of bank branches FTBNA agreed to purchase | number				13
Deposit Premium				3.32%
Branch Acquisition | As Recorded by FHN
Business Acquisition [Line Items]
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
Trustatlantic Financial Corporation
Business Acquisition [Line Items]
Acquisition date	Oct. 21, 2014
Number Of Bank Branches | number	5