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Significant Accounting Policies - Troubled Debt Restructurings and Allowance for Credit Loss Narrative (Details) - USD ($) | 9 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2022 | Dec. 31, 2022 | Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Percentage of Private Education Loans related to borrowers in school, grace or deferment |  | 24.00% | 24.00%
Interest rate offered to borrowers facing financial difficulty |  | 4.00% |
Interest rate offered to borrowers facing financial difficulty, period |  | 2 years |
Period of forbearance period to be classified as TDR |  | 3 months |
Period of forbearance |  | 24 months |
Period after grace period for forbearance allowance for loans |  | 9 months |
Forbearance period after grace period for loans |  | 6 months |
Monthly payment that is smaller than the interest accrued on the loan in that month |  | $ 25 |
Financing receivable allowance for credit loss, transfer to held-to-sale | $ 2,400,000 |  |
Credit Card |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Financing receivable allowance for credit loss, transfer to held-to-sale |  | $ 2,400,000 |

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- Definition Amount of expense reversal of allowance for credit loss on financing receivable transferred to held-for-sale classification. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 310 -Section 45 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=124265262&loc=SL120268815-111004 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522 + Details
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