Organization and Business - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Client	Dec. 31, 2022 USD ($)
Organization And Business [Line Items]
Loans, net	$ 54,827	$ 62,250
Private Education Loans [Member]
Organization And Business [Line Items]
Loans, net	16,902	18,725
FFELP Loans [Member]
Organization And Business [Line Items]
Loans, net	37,925	43,525
Federal Education Loans [Member]
Organization And Business [Line Items]
Loans, net	37,925	43,525
Federal Education Loans [Member] | FFELP Loans [Member]
Organization And Business [Line Items]
Loans, net	38,000
Consumer Lending [Member]
Organization And Business [Line Items]
Loans, net	16,902	$ 18,725
Consumer Lending [Member] | Private Education Loans [Member]
Organization And Business [Line Items]
Loans, net	17,000
Loans originated	$ 1,000
Business Processing [Member] | Minimum [Member]
Organization And Business [Line Items]
Number of clients for business processing services | Client	500