Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Loss reserves	$ 205	$ 58
Employee benefits	86	68
Accrued expenses	7	4
Lease liability	100	56
Federal loss carryforwards	44	44
State loss carryforwards	9	1
Other	20	19
Gross deferred tax assets	471	250
Deferred tax liabilities:
Depreciation and amortization	83	51
Investment in debt securities liabilities (ASC 320)	35	10
Equity investments	11	4
Other intangible assets	93	56
Prepaid expenses	15	10
ROU lease asset	89	50
Leasing	135	0
Other	10	0
Gross deferred tax liabilities	471	181
Net deferred tax assets	$ 0	$ 69

Deferred Tax Assets, Lease Liability

No definition available.

Name:	fhn_DeferredTaxAssetsLeaseLiability
Namespace Prefix:	fhn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from the provision for loan losses, which can only be deducted for tax purposes when actual loan losses are known, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken. Also includes losses associated with the repurchase obligations and other loss reserves.

+ References

No definition available.