Fair Value Measurements - Fair value of assets and liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Carrying Value
Financial Assets
Cash and cash equivalents	$ 164,023	$ 223,375
Mortgage notes receivable, net	814,454	798,486
Financial Liabilities
Accounts payable and accrued liabilities	8,542
Estimated Fair Value
Financial Assets
Cash and cash equivalents	164,023	223,375
Mortgage notes receivable, net	814,454	798,486
Financial Liabilities
Accounts payable and accrued liabilities	8,542
Level 1 | Estimated Fair Value
Financial Assets
Cash and cash equivalents	164,023	223,375
Level 2 | Estimated Fair Value
Financial Liabilities
Accounts payable and accrued liabilities	4,808
Level 3 | Estimated Fair Value
Financial Assets
Mortgage notes receivable, net	814,454	$ 798,486
Financial Liabilities
Accounts payable and accrued liabilities	$ 3,734