Fair Value Measurements - Schedule of Information on Assets and Liabilities Measured and Recorded at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets:
Loans held for sale, at fair value	$ 19,536
Loans held for investment, at fair value	951,990	$ 276,095
Mortgage servicing rights	9,786	9,238	$ 7,152
Derivative assets	1,261
Assets	1,019,731	310,124
Real estate owned, net	29,299	13,325
Liabilities:
Securitized debt, at fair value	669,139
Liabilities	669,139
Recurring Fair Value Measurements
Assets:
Loans held for sale, at fair value	19,536
Loans held for investment, at fair value	951,990	276,095
Mortgage servicing rights	9,786	9,238
Derivative assets	1,261
Assets	982,573	285,333
Liabilities:
Securitized debt, at fair value	669,139
Liabilities	669,139
Nonrecurring Fair Value Measurements
Assets:
Assets	37,158	24,791
Real estate owned, net	29,299	13,325
Individually evaluated/Impaired loans requiring specific allowance, net	7,859	11,466
Level 2
Assets:
Assets	20,797
Liabilities:
Liabilities	669,139
Level 2 | Recurring Fair Value Measurements
Assets:
Loans held for sale, at fair value	19,536
Derivative assets	1,261
Assets	20,797
Liabilities:
Securitized debt, at fair value	669,139
Liabilities	669,139
Level 3
Assets:
Assets	998,934	310,124
Level 3 | Recurring Fair Value Measurements
Assets:
Loans held for investment, at fair value	951,990	276,095
Mortgage servicing rights	9,786	9,238
Assets	961,776	285,333
Level 3 | Nonrecurring Fair Value Measurements
Assets:
Assets	37,158	24,791
Real estate owned, net	29,299	13,325
Individually evaluated/Impaired loans requiring specific allowance, net	$ 7,859	$ 11,466