Loans Receivable, Net - Net Book Value, Total Loan Exposure and Net Loan Exposure of Loans Receivable Based on Internal Risk Ratings (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024 USD ($) security_loan	Mar. 31, 2024 USD ($) loan	Dec. 31, 2023 USD ($) security_loan	Dec. 31, 2023 USD ($) loan	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans	173	173	178	178
Net Book Value	$ 23,189,312	$ 23,189,312	$ 23,787,012	$ 23,787,012
CECL reserve	(751,370)	(751,370)	(576,936)	(576,936)	$ (336,591)	$ (326,137)
Loans receivable, net	22,437,942	22,437,942	23,210,076	23,210,076
Total Loan Exposure	23,959,967	23,959,967	24,971,028	24,971,028
Net Loan Exposure	21,108,868	21,108,868	21,951,988	21,951,988
Principal balance	23,317,882	23,317,882	23,923,719	23,923,719
Total loan exposure including non-consolidated senior interests	742,600	742,600	1,100,000	1,100,000
Loan participations sold	335,280	335,280	337,721	337,721
Net loan exposure, asset-specific debt	1,100,000	1,100,000	1,000,000	1,000,000
Cost-recovery proceeds	57,900	57,900	53,000	53,000
Junior Loan Participation
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan participations sold	100,492	100,492	100,924	100,924
Senior Participations
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan participations sold	234,788	$ 234,788	236,797	$ 236,797
1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan		18		15
Net Book Value	791,251	$ 791,251	763,101	$ 763,101
Total Loan Exposure	839,963	839,963	811,217	811,217
Net Loan Exposure	791,925	$ 791,925	763,223	$ 763,223
2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan		34		36
Net Book Value	5,889,271	$ 5,889,271	6,143,184	$ 6,143,184
Total Loan Exposure	5,904,694	5,904,694	6,618,319	6,618,319
Net Loan Exposure	4,816,066	$ 4,816,066	5,095,395	$ 5,095,395
3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan		88		99
Net Book Value	11,425,297	$ 11,425,297	12,277,518	$ 12,277,518
Total Loan Exposure	11,750,476	11,750,476	12,573,282	12,573,282
Net Loan Exposure	11,075,625	$ 11,075,625	11,964,620	$ 11,964,620
4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan		16		15
Net Book Value	2,692,813	$ 2,692,813	2,725,930	$ 2,725,930
Total Loan Exposure	3,013,626	3,013,626	3,036,837	3,036,837
Net Loan Exposure	2,634,523	$ 2,634,523	2,668,025	$ 2,668,025
5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan		17		13
Net Book Value	2,390,680	$ 2,390,680	1,877,279	$ 1,877,279
Total Loan Exposure	2,451,208	2,451,208	1,931,373	1,931,373
Net Loan Exposure	$ 1,790,729	$ 1,790,729	$ 1,460,725	$ 1,460,725