Variable Interest Entities (Details) $ in Thousands	Jun. 30, 2020 USD ($) item	Jan. 31, 2020	Dec. 31, 2019 USD ($)
Variable interest entities
Total Assets	$ 79,556,279		$ 78,042,336
Total Liabilities	$ 74,691,483		72,905,322
Number of collateralized debt obligation | item	0
Investment in unconsolidated entities	$ 104,913		84,329
Primary beneficiary
Variable interest entities
Total Assets	64,175,387		62,187,175
Total Liabilities	62,617,975		$ 60,743,494
Equity interest		51.00%
Primary beneficiary | ASU 2015-02
Variable interest entities
Total Assets	1,100,000
Total Liabilities	585,100
Primary beneficiary | CMBS Venture Holdings
Variable interest entities
Total Assets	330,300
Total Liabilities	85,200
Equity interest			51.00%
Primary beneficiary | SPT Dolphin | ASU 2015-02
Variable interest entities
VIE assets	677,100
VIE liabilities	$ 445,900
Not primary beneficiary
Variable interest entities
Number of CDO structures currently in default | item	4
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	21,200
Not primary beneficiary | Securitization SPEs
Variable interest entities
Debt obligations to beneficial interest holders, unpaid principal balances	$ 4,100,000