Fair Value Measurements - Summary of Fair Value of Financial Assets and Liabilities (Details) - Fair Value Measurements Nonrecurring - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Carrying Value | Loans Held for Investment
Financial Assets
Financial Assets, Nonrecurring	$ 4,773,949	$ 4,456,460
Carrying Value | Collateralized Loan Obligation
Financial Liabilities
Financial Liabilities, Nonrecurring	2,821,233	1,825,568
Carrying Value | Secured Financing Agreements
Financial Liabilities
Financial Liabilities, Nonrecurring	858,640	1,514,028
Carrying Value | Mortgage Loan Payable
Financial Liabilities
Financial Liabilities, Nonrecurring	49,288	49,147
Estimate of Fair Value Measurement | Level III | Loans Held for Investment
Financial Assets
Financial Assets, Nonrecurring	4,779,484	4,472,984
Estimate of Fair Value Measurement | Level III | Collateralized Loan Obligation
Financial Liabilities
Financial Liabilities, Nonrecurring	2,819,640	1,834,760
Estimate of Fair Value Measurement | Level III | Secured Financing Agreements
Financial Liabilities
Financial Liabilities, Nonrecurring	850,558	1,532,910
Estimate of Fair Value Measurement | Level III | Mortgage Loan Payable
Financial Liabilities
Financial Liabilities, Nonrecurring	$ 49,288	$ 49,147