Borrowings - Unconsolidated VIEs Narrative (Details) - USD ($) $ in Thousands						12 Months Ended
	Jun. 28, 2024	Apr. 11, 2024	Apr. 09, 2024	Nov. 07, 2023	May 24, 2023	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Vertical risk retention interest						5.00%	5.00%
2024-R1 ABS transaction | Private Education Loans
Debt Instrument [Line Items]
Loans Transferred to the Trust by Third-Party Seller			$ 68,896
Additional Loans the Bank Transferred to the Trust			0
Gain on Sale for Additional Loans Transferred by Bank			$ 0
2024-B ABS transaction | Private Education Loans
Debt Instrument [Line Items]
Loans Transferred to the Trust by Third-Party Seller		$ 191,445
Additional Loans the Bank Transferred to the Trust		10,132
Gain on Sale for Additional Loans Transferred by Bank		$ 35
2024-D ABS transaction | Private Education Loans
Debt Instrument [Line Items]
Loans Transferred to the Trust by Third-Party Seller	$ 1,494,953
Additional Loans the Bank Transferred to the Trust	78,782
Gain on Sale for Additional Loans Transferred by Bank	$ 6,051
2023-B ABS transaction | Private Education Loans
Debt Instrument [Line Items]
Loans Transferred to the Trust by Third-Party Seller					$ 1,988,277
Additional Loans the Bank Transferred to the Trust					104,743
Gain on Sale for Additional Loans Transferred by Bank					$ 5,391
2023-D ABS transaction | Private Education Loans
Debt Instrument [Line Items]
Loans Transferred to the Trust by Third-Party Seller				$ 995,184
Additional Loans the Bank Transferred to the Trust				52,572
Gain on Sale for Additional Loans Transferred by Bank				$ 1,570