Investment Securities (Tables)

12 Months Ended

Dec. 31, 2020

Marketable Securities [Abstract]

Schedule of FHN's Investment Securities

The following tables summarize FHN’s investment securities on December 31, 2020 and 2019:

	December 31, 2020
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Securities available for sale:
U.S. treasuries	$	613	$	—	$	—	$	613
Government agency issued MBS	3,722		92		(2)		3,812
Government agency issued CMO	2,380		29		(3)		2,406
Other U.S. government agencies	672		12		—		684
Corporate and other debt	40		1		(1)		40
States and municipalities	445		15		—		460
	$	7,872	$	149	$	(6)	8,015
AFS securities recorded at fair value through earnings:
SBA-interest only strips (a)							32
Total securities available for sale (b)							$	8,047

(a)SBA-interest only strips are recorded at elected fair value. See Note 24 - Fair Value of Assets and Liabilities for additional information.

(b)Includes $6.4 billion of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes.

	December 31, 2019
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Securities available for sale:
U.S. treasuries	$	—	$	—	$	—	$	—
Government agency issued MBS	2,316		35		(3)		2,348
Government agency issued CMO	1,668		10		(7)		1,671
Other U.S. government agencies	304		4		(1)		307
Corporate and other debt	40		—		—		40
States and municipalities	57		3		—		60
	$	4,385	$	52	$	(11)	4,426
AFS securities recorded at fair value through earnings:
SBA-interest only strips (a)							19
Total securities available for sale (b)							$	4,445

(a)SBA-interest only strips are recorded at elected fair value. See Note 24 - Fair Value of Assets and Liabilities for additional information.

(b)Includes $3.8 billion of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes.

Schedule of Amortized Cost And Fair Value By Contractual Maturity

The amortized cost and fair value by contractual maturity for the available-for-sale debt securities portfolio on December 31, 2020 is provided below:

	Available for Sale
(Dollars in millions)	Amortized Cost		Fair Value
Within 1 year	$	756	$	758
After 1 year through 5 years	160		162
After 5 years through 10 years	184		192
After 10 years	670		717
Subtotal	1,770		1,829
Government agency issued MBS and CMO (a)	6,102		6,218
Total	$	7,872	$	8,047

(a)Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

Schedule of Investments Within The Available For Sale Portfolio That Had Unrealized Losses

The following tables provide information on investments within the available-for-sale portfolio that had unrealized losses as of December 31, 2020 and 2019:

	As of December 31, 2020
	Less than 12 months				12 months or longer				Total
(Dollars in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasuries	$	307	$	—	$	—	$	—	$	307	$	—
Government agency issued MBS	426		(2)		—		—		426		(2)
Government agency issued CMO	586		(3)		—		—		586		(3)
Other U.S. government agencies	80		(1)		—		—		80		(1)
States and municipalities	1		—		—		—		1		—
Total	$	1,400	$	(6)	$	—	$	—	$	1,400	$	(6)

	As of December 31, 2019
	Less than 12 months				12 months or longer				Total
(Dollars in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Government agency issued MBS	$	175	$	(1)	$	193	$	(2)	$	368	$	(3)
Government agency issued CMO	379		(2)		361		(5)		740		(7)
Other U.S. government agencies	98		(1)		—		—		98		(1)
States and municipalities	4		—		—		—		4		—
Total	$	656	$	(4)	$	554	$	(7)	$	1,210	$	(11)