Allowance for Credit Losses and Unfunded Loan Commitments - Age Analysis of Past Due Loans Delinquencies (Details) - USD ($)
$ in Thousands |
Sep. 30, 2026 |
Dec. 31, 2025 |
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Private Education Loans allowance for losses |
$ (1,449,614)
|
$ (1,430,318)
|
| Private Education Loans, net |
$ 20,626,170
|
$ 20,332,124
|
| Percentage of Private Education Loans in repayment, Year 1 |
60.80%
|
59.10%
|
| Percentage of Private Education Loans in repayment, Year 2 |
62.00%
|
63.60%
|
| Percentage of Private Education Loans in repayment, Year 3 |
67.80%
|
72.40%
|
| Percentage of Private Education Loans in repayment, Year 4 |
75.40%
|
79.40%
|
| Percentage of Private Education Loans in repayment, Year 5 |
81.20%
|
83.90%
|
| Percentage of Private Education Loans in repayment, After Year 5 |
89.10%
|
89.80%
|
| Percentage of Private Education Loans in repayment |
73.00%
|
73.40%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 1 |
0.20%
|
0.60%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 2 |
1.30%
|
1.50%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 3 |
3.80%
|
4.50%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 4 |
5.60%
|
4.90%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 5 |
6.00%
|
5.10%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, After Year 5 |
6.80%
|
6.80%
|
| Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment |
4.20%
|
4.00%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance, Year 1 |
0.20%
|
0.90%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance, Year 2 |
1.90%
|
3.60%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance, Year 3 |
3.30%
|
4.10%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance, Year 4 |
3.20%
|
3.60%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance, Year 5 |
2.90%
|
3.20%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance, After Year 5 |
2.20%
|
1.80%
|
| Loans in forbearance as a percentage of loans in repayment and forbearance |
2.30%
|
2.70%
|
| Consumer Portfolio Segment | Student Loan |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Total Private Education Loans in Repayment, Year 1 |
$ 2,081,093
|
$ 2,561,439
|
| Total Private Education Loans in Repayment, Year 2 |
3,159,368
|
3,458,164
|
| Total Private Education Loans in Repayment, Year 3 |
2,352,808
|
1,950,308
|
| Total Private Education Loans in Repayment, Year 4 |
1,562,664
|
1,812,638
|
| Total Private Education Loans in Repayment, Year 5 |
1,565,271
|
1,353,804
|
| Total Private Education Loans in Repayment, After Year 5 |
5,322,237
|
4,758,474
|
| Total Private Education Loans in repayment |
16,043,441
|
15,894,827
|
| Total Private Education Loans, gross, Year 1 |
3,422,456
|
4,331,374
|
| Total Private Education Loans, gross, Year 2 |
5,099,601
|
5,440,721
|
| Total Private Education Loans, gross, Year 3 |
3,471,818
|
2,693,020
|
| Total Private Education Loans, gross, Year 4 |
2,073,327
|
2,282,218
|
| Total Private Education Loans, gross, Year 5 |
1,928,580
|
1,613,592
|
| Total Private Education Loans, gross, After Year 5 |
5,970,235
|
5,299,509
|
| Total Private Education Loans, gross |
21,966,017
|
21,660,434
|
| Private Education Loans deferred origination costs and unamortized premium/(discount), Year 1 |
34,498
|
37,495
|
| Private Education Loans deferred origination costs and unamortized premium/(discount), Year 2 |
28,578
|
30,562
|
| Private Education Loans deferred origination costs and unamortized premium/(discount), Year 3 |
19,817
|
12,936
|
| Private Education Loans deferred origination costs and unamortized premium/(discount), Year 4 |
9,776
|
7,122
|
| Private Education Loans deferred origination costs and unamortized premium/(discount), Year 5 |
5,731
|
4,388
|
| Private Education Loans deferred origination costs and unamortized premium/(discount), After Year 5 |
11,367
|
9,505
|
| Private Education Loans deferred origination costs and unamortized premium/(discount) |
109,767
|
102,008
|
| Total Private Education Loans, Year 1 |
3,456,954
|
4,368,869
|
| Total Private Education Loans, Year 2 |
5,128,179
|
5,471,283
|
| Total Private Education Loans, Year 3 |
3,491,635
|
2,705,956
|
| Total Private Education Loans, Year 4 |
2,083,103
|
2,289,340
|
| Total Private Education Loans, Year 5 |
1,934,311
|
1,617,980
|
| Total Private Education Loans, After Year 5 |
5,981,602
|
5,309,014
|
| Total Private Education Loans |
22,075,784
|
21,762,442
|
| Private Education Loans allowance for losses, Year 1 |
(165,954)
|
(231,497)
|
| Private Education Loans allowance for losses, Year 2 |
(283,596)
|
(312,665)
|
| Private Education Loans allowance for losses, Year 3 |
(237,228)
|
(211,732)
|
| Private Education Loans allowance for losses, Year 4 |
(175,879)
|
(182,408)
|
| Private Education Loans allowance for losses, Year 5 |
(161,762)
|
(122,163)
|
| Private Education Loans allowance for losses, After Year 5 |
(425,195)
|
(369,853)
|
| Private Education Loans allowance for losses |
(1,449,614)
|
(1,430,318)
|
| Private Education Loans, net, Year 1 |
3,291,000
|
4,137,372
|
| Private Education Loans, net, Year 2 |
4,844,583
|
5,158,618
|
| Private Education Loans, net, Year 3 |
3,254,407
|
2,494,224
|
| Private Education Loans, net, Year 4 |
1,907,224
|
2,106,932
|
| Private Education Loans, net, Year 5 |
1,772,549
|
1,495,817
|
| Private Education Loans, net, After Year 5 |
5,556,407
|
4,939,161
|
| Private Education Loans, net |
20,626,170
|
20,332,124
|
| Consumer Portfolio Segment | Student Loan | Loan delinquent, current |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Year 1 |
2,076,858
|
2,545,734
|
| Year 2 |
3,119,754
|
3,404,837
|
| Year 3 |
2,263,785
|
1,863,481
|
| Year 4 |
1,475,033
|
1,723,538
|
| Year 5 |
1,471,230
|
1,284,830
|
| After Year 5 |
4,962,369
|
4,436,303
|
| Loan type |
15,369,029
|
15,258,723
|
| Consumer Portfolio Segment | Student Loan | Loan delinquent 30-59 days |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Year 1 |
3,082
|
10,981
|
| Year 2 |
23,998
|
29,336
|
| Year 3 |
46,900
|
41,888
|
| Year 4 |
43,645
|
44,106
|
| Year 5 |
46,944
|
33,983
|
| After Year 5 |
186,533
|
170,013
|
| Loan type |
351,102
|
330,307
|
| Consumer Portfolio Segment | Student Loan | Loan delinquent 60-89 days |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Year 1 |
809
|
3,267
|
| Year 2 |
9,920
|
13,265
|
| Year 3 |
23,447
|
22,287
|
| Year 4 |
25,206
|
22,729
|
| Year 5 |
25,450
|
17,118
|
| After Year 5 |
88,923
|
76,017
|
| Loan type |
173,755
|
154,683
|
| Consumer Portfolio Segment | Student Loan | Loan delinquent 90 days or greater past due |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Year 1 |
344
|
1,457
|
| Year 2 |
5,696
|
10,726
|
| Year 3 |
18,676
|
22,652
|
| Year 4 |
18,780
|
22,265
|
| Year 5 |
21,647
|
17,873
|
| After Year 5 |
84,412
|
76,141
|
| Loan type |
149,555
|
151,114
|
| Loans In-school/grace/deferment | Consumer Portfolio Segment | Student Loan |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Year 1 |
1,336,907
|
1,747,456
|
| Year 2 |
1,877,763
|
1,855,164
|
| Year 3 |
1,037,590
|
658,750
|
| Year 4 |
458,955
|
402,546
|
| Year 5 |
315,874
|
215,115
|
| After Year 5 |
526,055
|
453,501
|
| Loan type |
5,553,144
|
5,332,532
|
| Loans In forbearance | Consumer Portfolio Segment | Student Loan |
|
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] |
|
|
| Total Private Education Loans in forbearance, Year 1 |
4,456
|
22,479
|
| Total Private Education Loans in forbearance, Year 2 |
62,470
|
127,393
|
| Total Private Education Loans in forbearance, Year 3 |
81,420
|
83,962
|
| Total Private Education Loans in forbearance, Year 4 |
51,708
|
67,034
|
| Total Private Education Loans in forbearance, Year 5 |
47,435
|
44,673
|
| Total Private Education Loans in forbearance, After Year 5 |
121,943
|
87,534
|
| Total Private Education Loans in forbearance |
$ 369,432
|
$ 433,075
|