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Allowance for Credit Losses - Rollforward of Allowance for Credit Losses (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | $ 670 | $ 963 | $ 200 |
Charge-offs | (93) | (59) | (156) |
Recoveries | 34 | 57 | 36 |
Provision for credit losses | 95 | (310) | 503 |
Ending balance | 685 | 670 | 963 | $ 200
Loans and leases | 58,102 | 54,859 |  |
Accounting Standards Update [Extensible List] |  |  |  | Accounting Standards Update 2016-13 [Member]
Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 107 |
Ending balance |  |  |  | $ 107
Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 307 |
Ending balance |  |  |  | 307
Financial Asset Acquired with Credit Deterioration |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Additions in allowance for credit loss |  |  | 287 |
Funded and Unfunded Loan Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 736 | 1,048 |  |
Ending balance | 772 | 736 | 1,048 |
Funded Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Initial allowance on loans purchased with credit deterioration |  |  | 287 |
Provision for credit losses | 74 | (291) | 489 |
Unfunded Commitment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 66 | 85 | 6 |
Initial reserve on loans acquired |  |  | 41 |
Provision for credit losses | 21 | (19) | 14 |
Ending balance | 87 | 66 | 85 | 6
Unfunded Commitment | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 24 |
Ending balance |  |  |  | 24
Unfunded Commitment | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 30 |
Ending balance |  |  |  | 30
Commercial | C&I |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 334 | 453 | 123 |
Charge-offs | (62) | (34) | (129) |
Recoveries | 9 | 21 | 9 |
Ending balance | 308 | 334 | 453 | 123
Loans and leases | 31,781 | 31,068 |  |
Commercial | C&I | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 19 |
Ending balance |  |  |  | 19
Commercial | C&I | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 142 |
Ending balance |  |  |  | 142
Commercial | C&I | PCD Loans |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Charge-offs |  |  | (237) |
Commercial | C&I | Non-PCD Loans |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Provision for credit losses |  |  | 147 |
Commercial | C&I | Paycheck Protection Plan |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Loans and leases | 76 | 1,000 |  |
Commercial | C&I | Funded and Unfunded Loan Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 380 | 518 |  |
Ending balance | 363 | 380 | 518 |
Commercial | C&I | Funded Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Initial allowance on loans purchased with credit deterioration |  |  | 138 |
Provision for credit losses | 27 | (106) | 293 |
Commercial | C&I | Unfunded Commitment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 46 | 65 | 4 |
Initial reserve on loans acquired |  |  | 12 |
Provision for credit losses | 9 | (19) | 32 |
Ending balance | 55 | 46 | 65 | 4
Commercial | C&I | Unfunded Commitment | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 17 |
Ending balance |  |  |  | 17
Commercial | C&I | Unfunded Commitment | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 21 |
Ending balance |  |  |  | 21
Commercial | Commercial Real Estate |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 154 | 242 | 36 |
Charge-offs | (1) | (5) | (5) |
Recoveries | 1 | 5 | 4 |
Ending balance | 146 | 154 | 242 | 36
Loans and leases | 13,228 | 12,109 |  |
Commercial | Commercial Real Estate | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | (7) |
Ending balance |  |  |  | (7)
Commercial | Commercial Real Estate | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 29 |
Ending balance |  |  |  | 29
Commercial | Commercial Real Estate | Funded and Unfunded Loan Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 166 | 252 |  |
Ending balance | 168 | 166 | 252 |
Commercial | Commercial Real Estate | Funded Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Initial allowance on loans purchased with credit deterioration |  |  | 100 |
Provision for credit losses | (8) | (88) | 114 |
Commercial | Commercial Real Estate | Unfunded Commitment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 12 | 10 | 2 |
Initial reserve on loans acquired |  |  | 26 |
Provision for credit losses | 10 | 2 | (19) |
Ending balance | 22 | 12 | 10 | 2
Commercial | Commercial Real Estate | Unfunded Commitment | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 1 |
Ending balance |  |  |  | 1
Commercial | Commercial Real Estate | Unfunded Commitment | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 3 |
Ending balance |  |  |  | 3
Consumer |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Loans and leases | 12,253 | 10,772 |  |
Consumer | Consumer real estate |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 163 | 242 | 28 |
Charge-offs | (5) | (5) | (8) |
Recoveries | 19 | 27 | 18 |
Ending balance | 200 | 163 | 242 | 28
Loans and leases | 12,253 | 10,772 |  |
Consumer | Consumer real estate | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 93 |
Ending balance |  |  |  | 93
Consumer | Consumer real estate | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 121 |
Ending balance |  |  |  | 121
Consumer | Consumer real estate | Funded and Unfunded Loan Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 171 | 252 |  |
Ending balance | 210 | 171 | 252 |
Consumer | Consumer real estate | Funded Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Initial allowance on loans purchased with credit deterioration |  |  | 44 |
Provision for credit losses | 23 | (101) | 67 |
Consumer | Consumer real estate | Unfunded Commitment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 8 | 10 | 0 |
Initial reserve on loans acquired |  |  | 3 |
Provision for credit losses | 2 | (2) | 1 |
Ending balance | 10 | 8 | 10 | 0
Consumer | Consumer real estate | Unfunded Commitment | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 6 |
Ending balance |  |  |  | 6
Consumer | Consumer real estate | Unfunded Commitment | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 6 |
Ending balance |  |  |  | 6
Consumer | Credit card and other |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 19 | 26 | 13 |
Charge-offs | (25) | (15) | (14) |
Recoveries | 5 | 4 | 5 |
Ending balance | 31 | 19 | 26 | 13
Loans and leases | 840 | 910 |  |
Consumer | Credit card and other | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 2 |
Ending balance |  |  |  | 2
Consumer | Credit card and other | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 15 |
Ending balance |  |  |  | 15
Consumer | Credit card and other | Funded and Unfunded Loan Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 19 | 26 |  |
Ending balance | 31 | 19 | 26 |
Consumer | Credit card and other | Funded Commitments |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Initial allowance on loans purchased with credit deterioration |  |  | 5 |
Provision for credit losses | 32 | 4 | 15 |
Consumer | Credit card and other | Unfunded Commitment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance | 0 | 0 | 0 |
Initial reserve on loans acquired |  |  | 0 |
Provision for credit losses | 0 | 0 | 0 |
Ending balance | $ 0 | $ 0 | 0 | 0
Consumer | Credit card and other | Unfunded Commitment | Adjustment |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | 0 |
Ending balance |  |  |  | 0
Consumer | Credit card and other | Unfunded Commitment | Adjusted Balance |  |  |  |
Allowance for Loan and Lease Losses [Roll Forward] |  |  |  |
Beginning balance |  |  | $ 0 |
Ending balance |  |  |  | $ 0

X
- Definition Financing Receivable, Credit Loss, Initial Reserve on Loans Acquired + References No definition available. + Details
Name: | fhn_FinancingReceivableCreditLossInitialReserveOnLoansAcquired
Namespace Prefix: | fhn_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
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