Segment Reporting - Asset Information for Loans Segment (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Loans, net	$ 54,827	$ 62,250
Other	2,914	2,866
Total assets	61,375	70,795
Federal Education Loans [Member]
Segment Reporting Information [Line Items]
Loans, net	37,925	43,525
Cash and investments	1,520	2,746
Other	2,128	2,229
Total assets	41,573	48,500
Consumer Lending [Member]
Segment Reporting Information [Line Items]
Loans, net	16,902	18,725
Cash and investments	497	617
Other	577	453
Total assets	$ 17,976	$ 19,795