Fair Value Measurements - Fair value of assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Carrying Value
Financial Assets
Cash and cash equivalents	$ 54,964	$ 132,889
Mortgage notes receivable held for investment, net	881,950	901,350
Interest and fees receivable, net	14,775	17,526
Financial Liabilities
Senior unsecured notes	97,789	97,223
Private placement warrant liability	25	1,838
Estimated Fair Value
Financial Assets
Cash and cash equivalents	54,964	132,889
Mortgage notes receivable held for investment, net	865,304	901,350
Interest and fees receivable, net	14,775	17,526
Financial Liabilities
Senior unsecured notes	99,990	100,000
Private placement warrant liability	25	1,838
Level 1 | Estimated Fair Value
Financial Assets
Cash and cash equivalents	54,964	132,889
Financial Liabilities
Senior unsecured notes	99,990	100,000
Level 2 | Estimated Fair Value
Financial Assets
Interest and fees receivable, net	14,775	17,526
Financial Liabilities
Private placement warrant liability	25	1,838
Level 3 | Estimated Fair Value
Financial Assets
Mortgage notes receivable held for investment, net	$ 865,304	$ 901,350