Segment Reporting - Asset Information for Loans Segment (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Other	$ 2,616	$ 2,914
Total assets	56,622	61,375
Federal Education Loans [Member]
Segment Reporting Information [Line Items]
Loans, net	32,940	37,925
Cash and investments	2,518	1,520
Other	1,885	2,128
Total assets	37,343	41,573
Consumer Lending [Member]
Segment Reporting Information [Line Items]
Loans, net	16,238	16,902
Cash and investments	458	497
Other	547	577
Total assets	$ 17,243	$ 17,976