Loans Receivable, Net - Property Type and Geographic Distribution of Properties Securing Loans in Portfolio (Detail) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2025 USD ($) loan	Mar. 31, 2025 USD ($) security_loan	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($) loan	Dec. 31, 2024 USD ($) security_loan	Dec. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	138	138		130	130
Net book value	$ 19,049,712	$ 19,049,712	$ 19,049,712	$ 19,047,518	$ 19,047,518	$ 19,047,518
CECL reserve	(741,541)	(741,541)	(741,541)	(733,936)	(733,936)	(733,936)	$ (751,370)	$ (576,936)
Loans receivable, net	18,308,171	18,308,171	18,308,171	18,313,582	18,313,582	18,313,582
Net Loan Exposure	17,763,332	17,763,332	17,763,332	17,034,303	17,034,303	17,034,303
Cost-recovery proceeds	117,100	117,100	117,100	106,700	106,700	106,700
Loan participations sold	101,672	101,672	101,672	100,064	100,064	100,064
Asset-specific debt, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal balance	494,081	494,081	494,081	1,228,110	1,228,110	1,228,110
Junior Loan Participation
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan participations sold	$ 101,672	101,672	$ 101,672	$ 100,064	100,064	$ 100,064
Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			100.00%			100.00%
Subtotal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	106			100
Net book value	$ 11,493,988	11,493,988	$ 11,493,988	$ 12,430,396	12,430,396	$ 12,430,396
Net Loan Exposure	$ 10,491,465	10,491,465	$ 10,491,465	$ 10,537,164	10,537,164	$ 10,537,164
Subtotal | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			59.00%			62.00%
Sunbelt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	48			44
Net book value	$ 4,902,798	4,902,798	$ 4,902,798	$ 4,520,632	4,520,632	$ 4,520,632
Net Loan Exposure	$ 4,398,225	4,398,225	$ 4,398,225	$ 4,084,242	4,084,242	$ 4,084,242
Sunbelt | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			25.00%			24.00%
Northeast
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	21			21
Net book value	$ 3,252,180	3,252,180	$ 3,252,180	$ 4,614,582	4,614,582	$ 4,614,582
Net Loan Exposure	$ 3,022,630	3,022,630	$ 3,022,630	$ 3,452,961	3,452,961	$ 3,452,961
Northeast | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			17.00%			20.00%
West
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	22			21
Net book value	$ 1,935,719	1,935,719	$ 1,935,719	$ 1,865,382	1,865,382	$ 1,865,382
Net Loan Exposure	$ 1,814,883	1,814,883	$ 1,814,883	$ 1,746,309	1,746,309	$ 1,746,309
West | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			10.00%			10.00%
Midwest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	11			10
Net book value	$ 943,864	943,864	$ 943,864	$ 997,156	997,156	$ 997,156
Net Loan Exposure	$ 797,296	797,296	$ 797,296	$ 820,858	820,858	$ 820,858
Midwest | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			4.00%			5.00%
Northwest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	4			4
Net book value	$ 459,427	459,427	$ 459,427	$ 432,644	432,644	$ 432,644
Net Loan Exposure	$ 458,431	458,431	$ 458,431	$ 432,794	432,794	$ 432,794
Northwest | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			3.00%			3.00%
Subtotal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	32			30
Net book value	$ 7,555,724	7,555,724	$ 7,555,724	$ 6,617,122	6,617,122	$ 6,617,122
Net Loan Exposure	$ 7,271,867	7,271,867	$ 7,271,867	$ 6,497,139	6,497,139	$ 6,497,139
Subtotal | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			41.00%			38.00%
United Kingdom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	16			16
Net book value	$ 3,088,887	3,088,887	$ 3,088,887	$ 2,916,145	2,916,145	$ 2,916,145
Net Loan Exposure	$ 3,016,245	3,016,245	$ 3,016,245	$ 2,839,096	2,839,096	$ 2,839,096
United Kingdom | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			17.00%			17.00%
Ireland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3			3
Net book value	$ 1,115,753	1,115,753	$ 1,115,753	$ 1,050,276	1,050,276	$ 1,050,276
Net Loan Exposure	$ 1,110,602	1,110,602	$ 1,110,602	$ 1,048,329	1,048,329	$ 1,048,329
Ireland | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			6.00%			6.00%
Australia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	4			3
Net book value	$ 1,062,241	1,062,241	$ 1,062,241	$ 920,182	920,182	$ 920,182
Net Loan Exposure	$ 1,066,203	1,066,203	$ 1,066,203	$ 923,507	923,507	$ 923,507
Australia | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			6.00%			5.00%
Spain
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3			3
Net book value	$ 802,613	802,613	$ 802,613	$ 785,368	785,368	$ 785,368
Net Loan Exposure	$ 758,165	758,165	$ 758,165	$ 744,287	744,287	$ 744,287
Spain | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			4.00%			4.00%
Sweden
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1			1
Net book value	$ 473,437	473,437	$ 473,437	$ 429,084	429,084	$ 429,084
Net Loan Exposure	$ 473,728	473,728	$ 473,728	$ 429,724	429,724	$ 429,724
Sweden | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			2.00%			2.00%
Canada
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1
Net book value	$ 434,420	434,420	$ 434,420
Net Loan Exposure	$ 273,344	273,344	$ 273,344
Canada | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			2.00%
Other Europe
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3			3
Net book value	$ 517,620	517,620	$ 517,620	$ 455,417	455,417	$ 455,417
Net Loan Exposure	$ 512,645	512,645	$ 512,645	451,245	451,245	$ 451,245
Other Europe | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			4.00%			4.00%
Other International
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1
Net book value	$ 60,753	60,753	$ 60,753	60,650	60,650	$ 60,650
Net Loan Exposure	$ 60,935	60,935	$ 60,935	$ 60,951	60,951	$ 60,951
Other International | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			0.00%			0.00%
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	52			50
Net book value	$ 5,417,246	5,417,246	$ 5,417,246	$ 5,091,767	5,091,767	$ 5,091,767
Net Loan Exposure	$ 5,239,108	5,239,108	$ 5,239,108	$ 4,934,364	4,934,364	$ 4,934,364
Multifamily | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			30.00%			29.00%
Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	41			41
Net book value	$ 5,925,523	5,925,523	$ 5,925,523	$ 7,386,333	7,386,333	$ 7,386,333
Net Loan Exposure	$ 5,190,538	5,190,538	$ 5,190,538	$ 5,729,418	5,729,418	$ 5,729,418
Office | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			29.00%			33.00%
Hospitality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	17			16
Net book value	$ 2,857,777	2,857,777	$ 2,857,777	$ 2,768,374	2,768,374	$ 2,768,374
Net Loan Exposure	$ 2,745,468	2,745,468	$ 2,745,468	$ 2,663,349	2,663,349	$ 2,663,349
Hospitality | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			15.00%			16.00%
Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	14			11
Net book value	$ 2,590,953	2,590,953	$ 2,590,953	$ 2,030,627	2,030,627	$ 2,030,627
Net Loan Exposure	$ 2,558,417	2,558,417	$ 2,558,417	$ 2,000,831	2,000,831	$ 2,000,831
Industrial | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			14.00%			12.00%
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	5			5
Net book value	$ 605,745	605,745	$ 605,745	$ 555,553	555,553	$ 555,553
Net Loan Exposure	$ 581,280	581,280	$ 581,280	$ 532,069	532,069	$ 532,069
Retail | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			3.00%			3.00%
Self-storage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3
Net book value	$ 632,208	632,208	$ 632,208
Net Loan Exposure	$ 471,183	471,183	$ 471,183
Self-storage | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			3.00%
Life Sciences / Studio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3			3
Net book value	$ 341,401	341,401	$ 341,401	$ 342,817	342,817	$ 342,817
Net Loan Exposure	$ 335,452	335,452	$ 335,452	$ 337,687	337,687	$ 337,687
Life Sciences / Studio | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			2.00%			2.00%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3			4
Net book value	$ 678,859	678,859	$ 678,859	$ 872,047	872,047	$ 872,047
Net Loan Exposure	$ 641,886	$ 641,886	$ 641,886	$ 836,585	$ 836,585	$ 836,585
Other | Loan Exposure Risk | Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loan Exposure Percentage of Portfolio			4.00%			5.00%