Allowance for Credit Losses on Unfunded Loan Commitments - Allowance for Credit Losses and Recorded Investments in Loans (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Allowance | ||||
| Beginning balance | $ 66,015 | $ 52,541 | $ 77,132 | $ 84,568 |
| Provision | 153,230 | 154,758 | 269,616 | 255,743 |
| Transfer - funded loans | (125,541) | (109,422) | (253,044) | (242,434) |
| Unfunded loan commitments sold | 0 | 0 | 0 | 0 |
| Ending balance | 93,704 | 97,877 | 93,704 | 97,877 |
| Unfunded Commitments | ||||
| Beginning balance | 1,728,478 | 1,358,163 | 2,437,035 | 2,311,660 |
| Provision/New commitments - net | 4,850,608 | 4,251,598 | 7,795,793 | 6,755,182 |
| Transfer - funded loans | (3,335,053) | (2,936,392) | (6,431,011) | (6,393,473) |
| Unfunded loan commitments sold | (28,389) | 0 | (586,173) | 0 |
| Ending balance | 3,215,644 | 2,673,369 | 3,215,644 | 2,673,369 |
| Private Education Loans | ||||
| Allowance | ||||
| Beginning balance | 66,015 | 52,541 | 77,132 | 84,568 |
| Provision | 153,230 | 154,758 | 269,616 | 255,743 |
| Transfer - funded loans | (125,541) | (109,422) | (253,044) | (242,434) |
| Ending balance | 93,704 | 97,877 | 93,704 | 97,877 |
| Unfunded Commitments | ||||
| Ending balance | 2,544,083 | $ 2,673,369 | 2,544,083 | $ 2,673,369 |
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Unfunded loan commitments, classified as held for sale | $ 672,000 | $ 672,000 | ||