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Allowance for Loan Losses - Private Education Loan Portfolio Stratified by Key Credit Quality Indicators (Detail) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | --- | --- | ---
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Loan allowance for losses | $ (832) | $ (1,022) | $ (1,271) | $ (1,377)
Loans, net | 54,827 | 62,250 |  |
Private Education Loans [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Loans, gross | 17,519 | 19,525 | 21,180 |
Loan allowance for losses | (617) | (800) | $ (1,009) | $ (1,089)
Loans, net | 16,902 | 18,725 |  |
Loan, Net Charge-Offs in Year One | 0 |  |  |
Loan, Net Charge-Offs in Year Two | (7) |  |  |
Loan, Net Charge-Offs in Year Three | (10) |  |  |
Loan, Net Charge-Offs in Year Four | (5) |  |  |
Loan, Net Charge-Offs in Year Five | (7) |  |  |
Loan, Net Charge-Offs in Year Prior | (269) |  |  |
Total Charge-Offs | $ (298) |  |  |
Percentage of Loan, Net Charge-Offs | 100.00% |  |  |
FICO Scores [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | 1,756 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,642 | 4,614 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 4,020 | 1,538 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,269 | 1,467 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,211 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 8,551 | 9,602 |  |
Total Loans, gross | $ 17,519 | $ 19,525 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 100.00% | 100.00% |  |
FICO Scores [Member] | 640 and Above [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 815 | $ 1,721 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,575 | 4,529 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 3,898 | 1,515 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,240 | 1,426 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,162 | 529 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 7,132 | 8,107 |  |
Total Loans, gross | $ 15,822 | $ 17,827 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 90.00% | 91.00% |  |
FICO Scores [Member] | Below 640 [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 11 | $ 35 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 67 | 85 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 122 | 23 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 29 | 41 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 49 | 19 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 1,419 | 1,495 |  |
Total Loans, gross | $ 1,697 | $ 1,698 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 10.00% | 9.00% |  |
Loan Status [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | $ 1,756 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,642 | 4,614 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 4,020 | 1,538 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,269 | 1,467 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,211 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 8,551 | 9,602 |  |
Total Loans, gross | $ 17,519 | $ 19,525 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 100.00% | 100.00% |  |
Loan Status [Member] | School/Grace/Deferment [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 51 | $ 56 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 79 | 91 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 87 | 29 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 21 | 33 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 27 | 13 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 458 | 533 |  |
Total Loans, gross | $ 723 | $ 755 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 4.00% | 4.00% |  |
Loan Status [Member] | Current/90 Days or Less Delinquent [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 774 | $ 1,697 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,554 | 4,514 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 3,917 | 1,506 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,244 | 1,428 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,177 | 533 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 7,750 | 8,681 |  |
Total Loans, gross | $ 16,416 | $ 18,359 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 94.00% | 94.00% |  |
Loan Status [Member] | Greater than 90 days Delinquent [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 1 | $ 3 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 9 | 9 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 16 | 3 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 4 | 6 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 7 | 2 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 343 | 388 |  |
Total Loans, gross | $ 380 | $ 411 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 2.00% | 2.00% |  |
Seasoning [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | $ 1,756 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,642 | 4,614 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 4,020 | 1,538 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,269 | 1,467 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,211 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 8,551 | 9,602 |  |
Total Loans, gross | $ 17,519 | $ 19,525 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 100.00% | 100.00% |  |
Seasoning [Member] | 1-12 Payments [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 781 | $ 1,714 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 130 | 860 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 28 | 10 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 7 | 9 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 4 | 1 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 54 | 83 |  |
Total Loans, gross | $ 1,004 | $ 2,677 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 6.00% | 14.00% |  |
Seasoning [Member] | 13-24 Payments [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 0 | $ 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,453 | 3,699 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 812 | 147 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 12 | 31 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 13 | 6 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 62 | 91 |  |
Total Loans, gross | $ 2,352 | $ 3,974 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 13.00% | 20.00% |  |
Seasoning [Member] | 25-36 Payments [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 0 | $ 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 0 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 3,127 | 1,365 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 142 | 452 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 35 | 15 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 113 | 161 |  |
Total Loans, gross | $ 3,417 | $ 1,993 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 20.00% | 10.00% |  |
Seasoning [Member] | 37-48 Payments [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 0 | $ 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 0 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 0 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,097 | 957 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 388 | 132 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 179 | 260 |  |
Total Loans, gross | $ 1,664 | $ 1,349 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 9.00% | 7.00% |  |
Seasoning [Member] | More than 48 Payments [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 0 | $ 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 0 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 0 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 0 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 759 | 388 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 7,963 | 8,790 |  |
Total Loans, gross | $ 8,722 | $ 9,178 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 50.00% | 47.00% |  |
Seasoning [Member] | School/Grace/Deferment [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 45 | $ 42 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 59 | 55 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 53 | 16 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 11 | 18 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 12 | 6 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 180 | 217 |  |
Total Loans, gross | $ 360 | $ 354 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 2.00% | 2.00% |  |
Certain Loan Modifications [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | $ 1,756 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,642 | 4,614 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 4,020 | 1,538 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,269 | 1,467 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,211 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 8,551 | 9,602 |  |
Total Loans, gross | $ 17,519 | $ 19,525 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 100.00% | 100.00% |  |
Certain Loan Modifications [Member] | Modified Loans [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 0 | $ 11 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 41 | 71 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 130 | 34 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 46 | 68 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 82 | 37 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 5,775 | 6,447 |  |
Total Loans, gross | $ 6,074 | $ 6,668 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 35.00% | 34.00% |  |
Certain Loan Modifications [Member] | Non-modified Loans [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | $ 1,745 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,601 | 4,543 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 3,890 | 1,504 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,223 | 1,399 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,129 | 511 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 2,776 | 3,155 |  |
Total Loans, gross | $ 11,445 | $ 12,857 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 65.00% | 66.00% |  |
Cosigners [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | $ 1,756 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,642 | 4,614 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 4,020 | 1,538 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,269 | 1,467 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,211 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 8,551 | 9,602 |  |
Total Loans, gross | $ 17,519 | $ 19,525 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 100.00% | 100.00% |  |
Cosigners [Member] | With Cosigner [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 202 | $ 122 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 179 | 106 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 93 | 27 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 23 | 10 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 9 | 0 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 5,206 | 6,184 |  |
Total Loans, gross | $ 5,712 | $ 6,449 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 33.00% | 33.00% |  |
Cosigners [Member] | Without Cosigner [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 624 | $ 1,634 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,463 | 4,508 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 3,927 | 1,511 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,246 | 1,457 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,202 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 3,345 | 3,418 |  |
Total Loans, gross | $ 11,807 | $ 13,076 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 67.00% | 67.00% |  |
School Type [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 826 | $ 1,756 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,642 | 4,614 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 4,020 | 1,538 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,269 | 1,467 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,211 | 548 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 8,551 | 9,602 |  |
Total Loans, gross | $ 17,519 | $ 19,525 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 100.00% | 100.00% |  |
School Type [Member] | Not For Profit [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 777 | $ 1,655 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 1,555 | 4,347 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 3,786 | 1,470 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 1,213 | 1,366 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 1,126 | 503 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 7,225 | 8,026 |  |
Total Loans, gross | $ 15,682 | $ 17,367 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 90.00% | 89.00% |  |
School Type [Member] | For Profit [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Total Private Education Loan Credit Quality Indicators by Origination Year One | $ 49 | $ 101 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Two | 87 | 267 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Three | 234 | 68 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Four | 56 | 101 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Five | 85 | 45 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year Prior | 1,326 | 1,576 |  |
Total Loans, gross | $ 1,837 | $ 2,158 |  |
Total Private Education Loan Credit Quality Indicators by Origination Year, Percent | 10.00% | 11.00% |  |

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