Intangible Assets (Schedule Of Estimated Aggregate Amortization Expense for Intangible Assets) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2018	$ 26,174
2019	25,108
2020	21,422
2021	19,787
2022	$ 17,631

- 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

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

- 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

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

- 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

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

- 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

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

- 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

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

- References

No definition available.

+ Details

Name:	us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration