Loans - Activity in Portfolio (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) trust	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Apr. 30, 2021 USD ($)
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	$ 77,444
Credit loss allowance at the end of the period	67,270	$ 77,444
Activity in loan portfolio
Balance at the beginning of the period	12,139,908	11,470,224	$ 9,794,254
Acquisitions/originations/additional funding	13,990,579	5,337,399	9,094,714
Capitalized Interest	119,136	144,013	110,632
Basis of loans sold	(4,176,868)	(3,307,003)	(4,311,390)
Loan maturities/principal repayments	(4,197,809)	(1,821,196)	(3,304,838)
Discount accretion/premium amortization	57,948	42,199	35,387
Changes in fair value	69,050	133,124	71,601
Foreign currency translation gain/(loss), net	(72,130)	102,553	40,155
Credit loss reversal (provision), net	(4,633)	(46,091)	(7,126)
Loan foreclosures			(27,303)
Loan foreclosure and conversion to equity interest	(36,308)
Transfer to/from other asset classifications or between segments	524,776	105,126	(25,862)
Balance at the end of the period	18,413,649	12,139,908	11,470,224
Carrying Value	$ 18,480,919	12,217,352
Number of trusts redeemed | trust	3
90 days or greater past due | Non-Credit Deterioration
Activity in loan portfolio
Carrying Value	$ 456,500
Past due loan converted to equity interests	7,300
Cumulative Effect, Period of Adoption, Adjustment
Activity in loan portfolio
Balance at the beginning of the period		(20,440)
Balance at the end of the period			(20,440)
Total loans held-for-investment
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	77,444
Credit loss allowance at the end of the period	67,270	77,444
Activity in loan portfolio
Carrying Value	15,604,119	11,164,517
Total loans held-for-investment | First mortgage loan participation
Activity in loan portfolio
Carrying Value	12,991,099	8,931,772
Loans held-for-sale
Activity in loan portfolio
Balance at the beginning of the period	1,052,835	884,150	1,187,552
Acquisitions/originations/additional funding	5,351,034	2,204,203	3,636,380
Capitalized Interest	2,650	0	0
Basis of loans sold	(3,856,736)	(2,862,606)	(3,567,859)
Loan maturities/principal repayments	(352,711)	(142,644)	(162,376)
Discount accretion/premium amortization	504	110	2,841
Changes in fair value	67,864	148,506	72,915
Foreign currency translation gain/(loss), net	0	(1,291)	2,105
Credit loss reversal (provision), net	0	125	(1,196)
Loan foreclosures			0
Loan foreclosure and conversion to equity interest	0
Transfer to/from other asset classifications or between segments	611,360	822,282	(286,212)
Balance at the end of the period	2,876,800	1,052,835	884,150
Carrying Value	2,876,800	1,052,835
Loans held-for-sale | RMBS
Activity in loan portfolio
Transfer to/from other asset classifications or between segments		176,600
Loan held as secured borrowings
Activity in loan portfolio
Balance at the beginning of the period		0	74,346
Acquisitions/originations/additional funding			0
Capitalized Interest			0
Basis of loans sold			0
Loan maturities/principal repayments			(74,692)
Discount accretion/premium amortization			346
Changes in fair value			0
Foreign currency translation gain/(loss), net			0
Credit loss reversal (provision), net			0
Loan foreclosures			0
Transfer to/from other asset classifications or between segments			0
Balance at the end of the period			0
Funded commitments
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	77,444
Credit loss (reversal) provision, net	4,633
Charge-offs	(14,807)
Recoveries	0
Transfers	0
Credit loss allowance at the end of the period	67,270	77,444
Unfunded commitments
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	6,070
Credit loss (reversal) provision, net	767
Credit loss allowance at the end of the period	6,837	6,070
Unfunded commitments	2,252,028
Commercial Portfolio Segment
Activity in loan portfolio
Carrying Value	13,496,798
Commercial Portfolio Segment | Total loans held-for-investment
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	69,611
Credit loss allowance at the end of the period	46,600	69,611
Activity in loan portfolio
Balance at the beginning of the period	9,583,949	8,517,054	7,075,577
Acquisitions/originations/additional funding	7,822,441	2,753,782	4,161,584
Capitalized Interest	112,178	143,818	110,632
Basis of loans sold	(307,454)	(443,793)	(743,425)
Loan maturities/principal repayments	(3,508,969)	(1,398,991)	(2,172,068)
Discount accretion/premium amortization	52,416	39,642	30,128
Changes in fair value	0	0	0
Foreign currency translation gain/(loss), net	(71,419)	102,748	38,050
Credit loss reversal (provision), net	7,947	(48,711)	(2,616)
Loan foreclosures			(27,303)
Loan foreclosure and conversion to equity interest	(36,308)
Transfer to/from other asset classifications or between segments	(204,583)	(71,488)	46,495
Balance at the end of the period	13,450,198	9,583,949	8,517,054
Carrying Value	13,496,798	9,653,560
Commercial Portfolio Segment | Total loans held-for-investment | Cumulative Effect, Period of Adoption, Adjustment
Activity in loan portfolio
Balance at the beginning of the period		(10,112)
Balance at the end of the period			(10,112)
Commercial Portfolio Segment | Funded commitments
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	69,611
Credit loss (reversal) provision, net	(7,947)
Charge-offs	(14,807)
Recoveries	0
Transfers	257
Credit loss allowance at the end of the period	46,600	69,611
Commercial Portfolio Segment | Funded commitments | New York
Activity in allowance for loan losses
Charge-offs	(7,800)
Commercial Portfolio Segment | Funded commitments | Chicago
Activity in allowance for loan losses
Charge-offs	(7,000)
Commercial Portfolio Segment | Unfunded commitments
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	5,258
Credit loss (reversal) provision, net	1,434
Credit loss allowance at the end of the period	6,692	5,258
Unfunded commitments	2,236,598
Infrastructure Portfolio Segment
Activity in loan portfolio
Carrying Value	2,048,096
Infrastructure Portfolio Segment | Total loans held-for-investment
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	7,833
Credit loss allowance at the end of the period	20,670	7,833
Activity in loan portfolio
Balance at the beginning of the period	1,412,440	1,397,448	1,456,779
Acquisitions/originations/additional funding	817,104	278,694	902,053
Capitalized Interest	0	195	0
Basis of loans sold	(12,678)	0	0
Loan maturities/principal repayments	(304,878)	(189,288)	(832,998)
Discount accretion/premium amortization	5,028	2,447	2,072
Changes in fair value	0	0	0
Foreign currency translation gain/(loss), net	(711)	1,096	0
Credit loss reversal (provision), net	(12,580)	2,495	(3,314)
Loan foreclosures			0
Loan foreclosure and conversion to equity interest	0
Transfer to/from other asset classifications or between segments	123,701	(70,319)	(127,144)
Balance at the end of the period	2,027,426	1,412,440	1,397,448
Carrying Value	2,048,096	1,420,273
Infrastructure Portfolio Segment | Total loans held-for-investment | Cumulative Effect, Period of Adoption, Adjustment
Activity in loan portfolio
Balance at the beginning of the period		(10,328)
Balance at the end of the period			(10,328)
Infrastructure Portfolio Segment | Loans held-for-sale
Activity in loan portfolio
Carrying Value		120,540
Infrastructure Portfolio Segment | Funded commitments
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	7,833
Credit loss (reversal) provision, net	12,580
Charge-offs	0
Recoveries	0
Transfers	(257)
Credit loss allowance at the end of the period	20,670	7,833
Infrastructure Portfolio Segment | Unfunded commitments
Activity in allowance for loan losses
Credit loss allowance at beginning of the period	812
Credit loss (reversal) provision, net	(667)
Credit loss allowance at the end of the period	145	812
Unfunded commitments	15,430
Residential Portfolio Segment | 90 days or greater past due | Non-Credit Deterioration
Activity in loan portfolio
Carrying Value	28,400
Residential Portfolio Segment | New York
Activity in loan portfolio
Carrying Value				$ 100,500
Residential Portfolio Segment | First mortgage loan participation | New York
Activity in loan portfolio
Carrying Value				$ 29,000
Residential Portfolio Segment | Total loans held-for-investment
Activity in loan portfolio
Balance at the beginning of the period	90,684	671,572	0
Acquisitions/originations/additional funding	0	100,720	394,697
Capitalized Interest	4,308	0	0
Basis of loans sold	0	(604)	(106)
Loan maturities/principal repayments	(31,251)	(90,273)	(62,704)
Discount accretion/premium amortization	0	0	0
Changes in fair value	1,186	(15,382)	(1,314)
Foreign currency translation gain/(loss), net	0	0	0
Credit loss reversal (provision), net	0	0	0
Loan foreclosures			0
Loan foreclosure and conversion to equity interest	0
Transfer to/from other asset classifications or between segments	(5,702)	(575,349)	340,999
Balance at the end of the period	$ 59,225	$ 90,684	$ 671,572