Fair Value Measurements - Summary of Financial Assets and Liabilities Not Carried at Fair Value On Recurring Basis (Details) - Fair Value Measurements Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Carrying Value | CRE Debt Securities
Financial Assets
Financial Assets, Nonrecurring		$ 787,552
Carrying Value | Loans Held for Investment
Financial Assets
Financial Assets, Nonrecurring	$ 4,456,460	4,980,389
Carrying Value | Collateralized Loan Obligation
Financial Liabilities
Financial Liabilities, Nonrecurring	1,825,568	1,806,428
Carrying Value | Secured Financing Agreements
Financial Liabilities
Financial Liabilities, Nonrecurring	1,514,028	2,525,128
Carrying Value | Mortgage Loan Payable
Financial Liabilities
Financial Liabilities, Nonrecurring	49,147
Estimate of Fair Value Measurement | Level II | CRE Debt Securities
Financial Assets
Financial Assets, Nonrecurring		787,552
Estimate of Fair Value Measurement | Level III | Loans Held for Investment
Financial Assets
Financial Assets, Nonrecurring	4,472,984	5,004,379
Estimate of Fair Value Measurement | Level III | Collateralized Loan Obligation
Financial Liabilities
Financial Liabilities, Nonrecurring	1,834,760	1,806,428
Estimate of Fair Value Measurement | Level III | Secured Financing Agreements
Financial Liabilities
Financial Liabilities, Nonrecurring	1,532,910	$ 2,525,128
Estimate of Fair Value Measurement | Level III | Mortgage Loan Payable
Financial Liabilities
Financial Liabilities, Nonrecurring	$ 49,147