Goodwill - Summary of Goodwill for Each Reporting Units and Reportable Segments (Detail) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Goodwill [Line Items]
Goodwill	$ 428	$ 428
Consumer Lending Segment [Member]
Goodwill [Line Items]
Goodwill	196	196
Consumer Lending Segment [Member] \| Private Education Legacy In-School Loans [Member]
Goodwill [Line Items]
Goodwill	106	106
Consumer Lending Segment [Member] \| Private Education Refinance Loans [Member]
Goodwill [Line Items]
Goodwill	77	77
Consumer Lending Segment [Member] \| Private Education Recent In-School Loans [Member]
Goodwill [Line Items]
Goodwill	13	13
Federal Education Loans [Member]
Goodwill [Line Items]
Goodwill	232	232
Federal Education Loans [Member] \| FFELP Loans [Member]
Goodwill [Line Items]
Goodwill	227	227
Federal Education Loans [Member] \| Federal Education Loan Servicing [Member]
Goodwill [Line Items]
Goodwill	$ 5	$ 5

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details

- 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

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+ Details