Document And Entity Information	3 Months Ended
	Mar. 31, 2019 shares
Document And Entity Information [Abstract]
Entity Registrant Name	FIRST HORIZON NATIONAL CORP
Entity Central Index Key	0000036966
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding (in shares)	315,361,125
Trading Symbol - Common	FHN
Entity Emerging Growth Company	false
Entity Small Business	false