Variable Interest Entities - Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) collateralizedLoanObligation loans	Dec. 31, 2020 USD ($)
Variable interest entities
Number of CLOs | collateralizedLoanObligation	3
Number of SASBs | loans	1
Assets	$ 81,980,864	$ 80,873,509
Liabilities	77,133,752	76,010,933
Investment in unconsolidated entities	$ 94,000	$ 108,054
CMBS JV
Variable interest entities
Ownership percentage	51.00%
Primary beneficiary | ASU 2015-02
Variable interest entities
Assets	$ 102,000
Liabilities	53,500
Primary beneficiary | CMBS Venture Holdings
Variable interest entities
Assets	326,500
Liabilities	73,600
Primary beneficiary | SPT Dolphin | ASU 2015-02
Variable interest entities
Assets	659,600
Liabilities	523,100
Not primary beneficiary
Variable interest entities
Maximum risk of loss related to VIEs, on fair value basis	23,500
Not primary beneficiary | ASU 2015-02 | Measurement Period Adjustments
Variable interest entities
Investment in unconsolidated entities	26,600
Not primary beneficiary | Securitization SPEs
Variable interest entities
Long term debt, gross	$ 4,900,000