Restricted Cash, Other Assets and Accrued and Other Liabilities - Summary of Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 73,059	$ 126,065	$ 139,549	$ 110,146
Borrower escrow deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	37,642	74,496
Real estate escrow reserves
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	18,469	18,020
Working capital and other reserves
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	6,850	4,198
Capital expenditure reserves
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	6,653	8,882
Margin pledged as collateral
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	2,633	19,536
Tenant lockboxes
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 812	$ 933