Other Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Other Events	Other EventsIssuance of Series F Preferred StockOn May 3, 2021, FHN issued 1,500 shares having an aggregate liquidation preference of $150 million of Series F Non-Cumulative Perpetual Preferred Stock for net proceeds of approximately $146 million. Dividends on the Series F Preferred Stock, if declared, accrue and are payable quarterly, in arrears, at a rate of 4.70% per annum. For the issuance, FHN issued depositary shares, each of which represents a fractional ownership interest in a share of FHN's preferred stock.