Acquisitions and Divestitures (Narrative) (Details) $ in Thousands	9 Months Ended	10 Months Ended
	Oct. 02, 2015 USD ($) shares	Oct. 27, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 16, 2016 USD ($)	Dec. 31, 2015 USD ($)	[1]	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Goodwill			$ 191,371		$ 191,307		$ 145,932	$ 145,932
Trustatlantic Financial Corporation
Business Acquisition [Line Items]
Acquisition date	Oct. 02, 2015
Business Acquisition, Name of Acquired Entity	TrustAtlantic Financial Corporation
Business Acquisition, Description of Acquired Entity	Prior to the acquisition TAB had five branches located in Raleigh, Cary and Greenville, North Carolina.
Number of common shares issued in acquisition | shares	5,093,657
Number Of Bank Branches	5
Coastal Securities
Business Acquisition [Line Items]
Expected cash payment to acquire business, gross		$ 160,000
As Recorded by FHN | Trustatlantic Financial Corporation
Business Acquisition [Line Items]
Cash payment to acquire business, gross	$ 23,900
Total transaction value	96,700
Assets acquired	400,000
Loans acquired	281,900
Deposits assumed	344,000
Goodwill	45,400
As Acquired [Member] | Trustatlantic Financial Corporation
Business Acquisition [Line Items]
Loans acquired	$ 298,100
As Acquired [Member] | GE Capital Member [Member]
Business Acquisition [Line Items]
Loans acquired				$ 537,400

[1] The increase in goodwill was related to the TAF acquisition in fourth quarter 2015.