Goodwill and Other Intangible Assets - Schedule Of Estimated Aggregate Amortization Expense for Intangible Assets (Details) $ in Millions	Dec. 31, 2020 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 56
2022	51
2023	48
2024	44
2025	$ 37

- Definition

Amount of amortization expense expected to be recognized during the next fiscal year following the latest fiscal year for assets, including financial assets, excluding goodwill, with a finite life.

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense expected to be recognized during the fourth fiscal year following the latest fiscal year for assets, including financial assets, excluding goodwill, with a finite life.

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense expected to be recognized during the third fiscal year following the latest fiscal year for assets, including financial assets, excluding goodwill, with a finite life.

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense expected to be recognized during the fifth fiscal year following the latest fiscal year for assets, including financial assets, excluding goodwill, with a finite life.

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense expected to be recognized during the second fiscal year following the latest fiscal year for assets, including financial assets, excluding goodwill, with a finite life.

+ References

No definition available.

+ Details

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Namespace Prefix:	fhn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- References

No definition available.

+ Details

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