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Allowance for Loan Losses - Loan Type (Detail) - FFELP Loans [Member] - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020
Financing Receivable Recorded Investment Past Due [Line Items] |  |
Total loans, gross | $ 55,827 | $ 61,223
Change | (5,396) |
Stafford Loans [Member] |  |
Financing Receivable Recorded Investment Past Due [Line Items] |  |
Total loans, gross | 16,996 | 18,364
Change | (1,368) |
Consolidation Loans [Member] |  |
Financing Receivable Recorded Investment Past Due [Line Items] |  |
Total loans, gross | 34,011 | 37,829
Change | (3,818) |
Rehab Loans [Member] |  |
Financing Receivable Recorded Investment Past Due [Line Items] |  |
Total loans, gross | 4,820 | $ 5,030
Change | $ (210) |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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- Details
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