Summary of Significant Accounting Policies - Classification, Carrying Value and Maximum Exposure of VIEs (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Real estate securities, available for sale, at fair value	$ 36,250	$ 252,824
Investments in unconsolidated ventures	424,557	595,305
Loans and preferred equity held for investment, net	2,103,414	2,576,332
Total Assets	6,511,657	$ 7,414,306
Unconsolidated VIEs
Variable Interest Entity [Line Items]
Real estate securities, available for sale, at fair value	36,250
Investments in unconsolidated ventures	349,635
Loans and preferred equity held for investment, net	13,638
Total Assets	399,523
Maximum Exposure to Loss	419,876
Unconsolidated VIEs \| Real estate securities, available for sale
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	31,959
Unconsolidated VIEs \| Investments in unconsolidated ventures
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	374,279
Unconsolidated VIEs \| Loans and preferred equity held for investment, net
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	$ 13,638

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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