Loans Held for Investment - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Jul. 01, 2006	Jun. 30, 2006	Sep. 30, 1993
Receivables [Abstract]
Percent of private loans indexed to LIBOR	42.00%		45.00%
Tier 1 of government guarantee (at least)	97.00%			97.00%
Tier 2 of government guarantee					98.00%
Tier 3 of government guarantee						100.00%
Gain on sales of loans, net	$ (9,000)	$ 9,881,000
Proceeds from sale of loans receivable	$ 0	95,000,000
Net proceeds from sales of loans held for investment, principal		89,000,000
Net proceeds from sales of loans held for investment, capitalized interest		$ 6,000,000
Estimated weighted average life of student loans	5 years		5 years