Borrowings - Summary of Exposure Related To Unconsolidated VIEs (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Estimated Fair Value	$ 2,283,262		$ 2,411,622
Total Exposure	49,479	$ 32,034	112,962	$ 62,600	$ 32,720	$ 124,924
Variable Interest Entity, Not Primary Beneficiary | Private Education Loan term securitizations
Debt Instrument [Line Items]
Estimated Fair Value	602,539		423,327
Equity Interests	60,473		54,481
Total Exposure	$ 663,012		$ 477,808