Commercial Mortgage Loans, Subordinate Loans and Other Lending Assets, Net - Activity Relating to Loan Investment Portfolio (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Principal Balance
Principal value, beginning balance	$ 7,890,848
Principal value, ending balance	8,960,722
Specific CECL Allowance
Specific provision for loan loss, beginning	(145,000)
Specific provision for loan loss, ending	(172,000)
Carry Value, Net
General CECL allowance	(23,362)		$ (33,588)
Carrying value, net	8,937,360		7,857,260
General CECL Allowance on unfunded commitments	3,999	$ 3,928	3,106	$ 2,444	$ 3,794	$ 3,365
Commercial Mortgage and Subordinated Portfolio Segment
Principal Balance
Principal value, beginning balance	8,072,377
New funding of loans	2,326,545
Add-on loan fundings	334,094
Loan repayments and sales	(1,191,375)
Gain (loss) on foreign currency translation	(368,401)
PIK interest and amortization of fees	11,653
Principal value, ending balance	9,184,893
Deferred Fees/Other Items
Deferred fees/other items, beginning	(36,529)
Gain (loss) on foreign currency translation	3,714
Deferred fees and other items	(34,907)
PIK interest and amortization of fees	15,551
Deferred fees/other items, ending	(52,171)
Specific CECL Allowance
Specific provision for loan loss, beginning	(145,000)
Specific provision for loan loss, ending	(172,000)
Carry Value, Net
Carrying value, beginning balance	7,890,848
New funding of loans	2,326,545
Add-on loan fundings	334,094
Loan repayments and sales	(1,191,375)
Gain (loss) on foreign currency translation	(364,687)
Specific CECL Allowance, net	(27,000)
Deferred fees and other items	(34,907)
PIK interest and amortization of fees	27,204
Carrying value, ending balance	8,960,722
Carrying value, net	$ 11,000		$ 97,800