Variable Interest Entity (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Variable Interest Entities
Carrying amount of loans and investments before reserves related to VIEs	$ 5,475,082
Loan loss reserves related to VIEs	148,329	$ 71,069	$ 71,069	$ 62,783
Assets:
Restricted cash	197,470	210,875	$ 180,606	$ 139,398
Loans and investments, net	5,285,868	4,189,960
Other assets	182,044	125,788
Total assets	7,660,986	6,239,160
Liabilities:
Collateralized loan obligations	2,517,309	2,130,121
Debt fund		68,629
Other liabilities	197,644	134,299
Total liabilities	6,178,301	4,883,133
Consolidated variable interest entities
Assets:
Total assets	3,134,447	2,784,756
Liabilities:
Total liabilities	2,520,064	2,209,599
CLOs and Debt Fund
Assets:
Restricted cash	188,226	208,467
Loans and investments, net	2,923,634	2,557,909
Other assets	22,587	18,380
Total assets	3,134,447	2,784,756
Liabilities:
Collateralized loan obligations	2,517,309	2,130,121
Debt fund		68,629
Other liabilities	2,755	10,849
Total liabilities	$ 2,520,064	$ 2,209,599
Unconsolidated VIEs
Variable Interest Entities
Number of VIEs where the reporting entity is not VIE's primary beneficiary and VIEs have variable interest | item	32
Carrying amount of loans and investments before reserves related to VIEs	$ 219,600
Loan loss reserves related to VIEs	86,900
Exposure to real estate debt	4,410,000
Assets:
Total assets	540,903
Loans | Unconsolidated VIEs
Assets:
Total assets	419,558
B Piece bonds | Unconsolidated VIEs
Assets:
Total assets	58,460
APL certificates | Unconsolidated VIEs
Assets:
Total assets	38,708
Equity investments | Unconsolidated VIEs
Assets:
Total assets	12,804
SFR bonds | Unconsolidated VIEs
Assets:
Total assets	10,000
Agency interest only strips | Unconsolidated VIEs
Assets:
Total assets	$ 1,373