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Loans Receivable, Net - Net Book Value, Total Loan Exposure and Net Loan Exposure of Loans Receivable Based on Internal Risk Ratings (Detail) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2025 USD ($) loan	Sep. 30, 2025 USD ($) security_loan	Dec. 31, 2024 USD ($) loan	Dec. 31, 2024 USD ($) security_loan	Jun. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans	137	137	130	130
Net book value	$ 18,066,919	$ 18,066,919	$ 19,047,518	$ 19,047,518
CECL reserve	(695,719)	(695,719)	(733,936)	(733,936)	$ (740,851)	$ (741,541)	$ (1,011,059)	$ (893,938)	$ (751,370)	$ (576,936)
Loans receivable, net	17,371,200	17,371,200	18,313,582	18,313,582
Net loan exposure	16,793,738	16,793,738	17,034,303	17,034,303
Cost-recovery proceeds	69,200	69,200	106,700	106,700
Loan participations sold	0	0	100,064	100,064
Junior Loan Participation
Financing Receivable, Credit Quality Indicator [Line Items]
Loan participations sold			100,064	100,064
Asset-specific debt, net
Financing Receivable, Credit Quality Indicator [Line Items]
Principal balance	$ 629,890	629,890	$ 1,228,110	1,228,110
1
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans | loan	6		11
Net book value	$ 409,199	409,199	$ 1,919,280	1,919,280
Net loan exposure	$ 408,355	408,355	$ 994,056	994,056
2
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans | loan	22		21
Net book value	$ 3,173,245	3,173,245	$ 3,346,881	3,346,881
Net loan exposure	$ 3,007,691	3,007,691	$ 3,349,347	3,349,347
3
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans | loan	80		65
Net book value	$ 10,578,120	10,578,120	$ 9,246,692	9,246,692
Net loan exposure	$ 10,087,715	10,087,715	$ 8,818,346	8,818,346
4
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans | loan	17		20
Net book value	$ 2,732,203	2,732,203	$ 2,707,104	2,707,104
Net loan exposure	$ 2,619,771	2,619,771	$ 2,622,877	2,622,877
5
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans | loan	12		13
Net book value	$ 1,174,152	1,174,152	$ 1,827,561	1,827,561
Net loan exposure	$ 670,206	$ 670,206	$ 1,249,677	$ 1,249,677

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