Segment Reporting - Asset Information for Loans Segment (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Other	$ 2,911	$ 3,223
Total assets	78,158	80,605
Federal Education Loans [Member]
Segment Reporting Information [Line Items]
Loans, net	51,013	52,641
Cash and investments	1,879	2,071
Other	2,008	2,183
Total assets	54,900	56,895
Consumer Lending [Member]
Segment Reporting Information [Line Items]
Loans, net	20,088	20,171
Cash and investments	774	824
Other	720	815
Total assets	$ 21,582	$ 21,810