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Allowance for Loan Losses - Age Analysis of Past Due Loans Delinquencies (Detail) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2020 | Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2019
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loan allowance for losses | $ (1,253) | $ (1,400) | $ (1,377) | $ (1,274) | $ (1,394) | $ (1,112)
FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 55,827 | 61,223 |  |  |  |
Loan allowance for losses | (277) | (302) | (288) | $ (282) | $ (311) | $ (64)
Loans, net | 55,550 |  | 58,284 |  |  |
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 7,583 | 8,748 | 8,431 |  |  |
Loan allowance for losses | (826) | (933) | (929) |  |  |
Loans, net | $ 6,757 | $ 7,815 | $ 7,502 |  |  |
Dimensions of concentration risk | 100.00% | 100.00% | 100.00% |  |  |
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | $ 13,118 | $ 13,812 | $ 13,737 |  |  |
Loan allowance for losses | (150) | (165) | (160) |  |  |
Loans, net | $ 12,968 | $ 13,647 | $ 13,577 |  |  |
Dimensions of concentration risk | 100.00% | 100.00% | 100.00% |  |  |
Credit Concentration Risk [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | $ 55,827 | $ 61,223 | $ 58,572 |  |  |
Loan allowance for losses | (277) | (302) | (288) |  |  |
Loans, net | $ 55,550 | $ 60,921 | $ 58,284 |  |  |
Dimensions of concentration risk | 100.00% | 100.00% | 100.00% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 2.70% | 1.50% | 2.50% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 0.20% | 0.10% | 0.20% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 3.00% | 2.90% | 2.90% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 1.40% | 1.10% | 1.50% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 0.10% | 0.10% | 0.10% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 1.50% | 1.50% | 1.70% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 2.60% | 2.60% | 2.60% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 0.10% | 0.20% | 0.10% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent, percentage | 3.80% | 3.80% | 4.60% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Current [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 93.30% | 94.80% | 93.40% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Current [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 99.60% | 99.60% | 99.60% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Current [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 91.70% | 91.80% | 90.80% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 90.30% | 82.30% | 88.30% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 97.90% | 94.10% | 97.50% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Loans In Repayment [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 82.10% | 69.60% | 82.00% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Delinquent Loans in Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 6.70% | 5.20% | 6.60% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Delinquent Loans in Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 0.40% | 0.40% | 0.40% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Delinquent Loans in Repayment [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 8.30% | 8.20% | 9.20% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Forbearance, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 7.00% | 14.80% | 8.60% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Forbearance, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 0.70% | 4.40% | 1.00% |  |  |
Credit Concentration Risk [Member] | Financing Receivables, Forbearance, Loans In Repayment [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Dimensions of concentration risk | 13.90% | 26.60% | 13.80% |  |  |
School/Grace/Deferment [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | $ 220 | $ 293 | $ 280 |  |  |
School/Grace/Deferment [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 183 | 219 | 203 |  |  |
School/Grace/Deferment [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 2,576 | 3,130 | 2,791 |  |  |
Forbearance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 517 | 1,253 | 703 |  |  |
Forbearance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 89 | 594 | 141 |  |  |
Forbearance [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Total Loans, gross | 7,397 | 15,453 | 7,725 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans current | 6,387 | 6,827 | 6,952 |  |  |
Total Loans, gross | 6,846 | 7,202 | 7,448 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans current | 12,800 | 12,948 | 13,335 |  |  |
Total Loans, gross | 12,846 | 12,999 | 13,393 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans current | 42,026 | 39,152 | 43,623 |  |  |
Total Loans, gross | 45,854 | 42,640 | 48,056 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 186 | 110 | 185 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 22 | 18 | 26 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 1,398 | 1,222 | 1,374 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 95 | 77 | 114 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 9 | 11 | 12 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 685 | 657 | 836 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 178 | 188 | 197 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDRs [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | 15 | 22 | 20 |  |  |
Repayment [Member] | Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | FFELP Loans [Member] |  |  |  |  |  |
Loans in repayment and percentage of each status: |  |  |  |  |  |
Loans delinquent | $ 1,745 | $ 1,609 | $ 2,223 |  |  |

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