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Loans and Allowance for Loan Losses - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023 | Jun. 30, 2024 | Jun. 30, 2023 | Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans | $ 43,120,674,000 |  | $ 43,120,674,000 |  | $ 43,404,490,000 |  |  |
Land held for future development, period |  |  | 1 year |  |  |  |  |
Financing receivable, allowance for credit loss | 484,985,000 | $ 477,532,000 | $ 484,985,000 | $ 477,532,000 | 479,385,000 | $ 485,101,000 | $ 471,238,000 | $ 443,424,000
Reserve for unfunded commitments | 49,600,000 |  | 49,600,000 |  | 57,200,000 |  |  |
All financing receivable, allowance for credit loss | $ 534,500,000 |  | 534,500,000 |  | $ 536,600,000 |  |  |
Increase (decrease) in allowance for credit loss |  |  | $ (2,100,000) |  |  |  |  |
ACL to loans ratio (as percent) | 1.24% |  | 1.24% |  | 1.24% |  |  |
Allowance for credit loss, reasonable and supportable forecast period (in year) |  |  | 2 years |  |  |  |  |
Allowance for credit loss, straight-line basis historical period (in year) |  |  | 1 year |  |  |  |  |
Allowance for credit loss, measurement input, estimated peak weighted average unemployment rate | 4.50% |  | 4.50% |  | 4.50% |  |  |
Financing receivable, modified, subsequent default | $ 0 | 0 | $ 74,700,000 | 0 |  |  |  |
Commitments to land additional funds to TDRs | 0 |  | 0 |  | $ 0 |  |  |
Total consumer |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Charge-off of previously established reserves for credit losses associated with the transfer to held for sale |  | 23,300,000 |  | 31,300,000 | 31,300,000 |  |  |
Reclassification to held-for-sale |  | 1,170,000,000 |  | 1,590,000,000 |  |  |  |
Financing receivable, allowance for credit loss | 141,329,000 | $ 134,702,000 | $ 141,329,000 | $ 134,702,000 | 126,657,000 | $ 122,691,000 | $ 141,525,000 | $ 138,299,000
Substandard |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Retail loan substandard period (in days) |  |  | 90 days |  |  |  |  |
Loss |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Retail loan charge off (in days) |  |  | 120 days |  |  |  |  |
Asset Pledged as Collateral |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans | $ 24,800,000,000 |  | $ 24,800,000,000 |  | $ 24,310,000,000 |  |  |

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