Loans Receivable, Net - Property Type and Geographic Distribution of Properties Securing Loans in Portfolio (Detail) $ in Thousands	Dec. 31, 2021 USD ($) SecurityLoan	Dec. 31, 2020 USD ($) SecurityLoan	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	188	120
Principal balance	$ 22,003,017	$ 16,572,715	$ 16,164,801
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	(124,679)	(173,549)	$ 0
Loans receivable, net	21,878,338	16,399,166
Total Loan Exposure	$ 23,669,111	$ 17,454,621
Percentage of portfolio	100.00%	100.00%
Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	65	59
Principal balance	$ 9,473,039	$ 9,980,799
Total Loan Exposure	$ 10,425,026	$ 10,451,658
Percentage of portfolio	44.00%	59.00%
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	75	31
Principal balance	$ 5,721,260	$ 1,788,149
Total Loan Exposure	$ 5,771,517	$ 1,862,667
Percentage of portfolio	24.00%	11.00%
Hospitality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	25	14
Principal balance	$ 3,427,245	$ 2,295,255
Total Loan Exposure	$ 3,540,391	$ 2,369,454
Percentage of portfolio	15.00%	14.00%
Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	6	6
Principal balance	$ 1,102,452	$ 673,912
Total Loan Exposure	$ 1,185,606	$ 675,344
Percentage of portfolio	5.00%	4.00%
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	8	4
Principal balance	$ 871,241	$ 538,702
Total Loan Exposure	$ 909,970	$ 551,243
Percentage of portfolio	4.00%	3.00%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	9	6
Principal balance	$ 1,407,780	$ 1,295,898
Total Loan Exposure	$ 1,836,601	$ 1,544,255
Percentage of portfolio	8.00%	9.00%
Subtotal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	156	94
Principal balance	$ 15,357,571	$ 11,203,765
Total Loan Exposure	$ 16,706,378	$ 11,780,800
Percentage of portfolio	71.00%	68.00%
Sunbelt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	71	33
Principal balance	$ 5,907,230	$ 2,902,996
Total Loan Exposure	$ 6,206,216	$ 2,986,221
Percentage of portfolio	26.00%	17.00%
Northeast
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	37	25
Principal balance	$ 4,615,076	$ 4,369,537
Total Loan Exposure	$ 4,934,295	$ 4,389,384
Percentage of portfolio	21.00%	25.00%
West
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	33	27
Principal balance	$ 3,520,942	$ 2,942,126
Total Loan Exposure	$ 4,199,208	$ 3,413,089
Percentage of portfolio	18.00%	20.00%
Midwest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	10	8
Principal balance	$ 1,063,202	$ 973,702
Total Loan Exposure	$ 1,113,959	$ 976,693
Percentage of portfolio	5.00%	6.00%
Northwest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	5	1
Principal balance	$ 251,121	$ 15,404
Total Loan Exposure	$ 252,700	$ 15,413
Percentage of portfolio	1.00%	0.00%
Subtotal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	32	26
Principal balance	$ 6,645,446	$ 5,368,950
Total Loan Exposure	$ 6,962,733	$ 5,673,821
Percentage of portfolio	29.00%	32.00%
United Kingdom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	17	13
Principal balance	$ 2,342,146	$ 1,816,901
Total Loan Exposure	$ 2,598,033	$ 2,066,390
Percentage of portfolio	11.00%	12.00%
Spain
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	4	2
Principal balance	$ 1,374,364	$ 1,247,162
Total Loan Exposure	$ 1,380,763	$ 1,252,080
Percentage of portfolio	6.00%	7.00%
Ireland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	1	1
Principal balance	$ 1,210,375	$ 1,309,443
Total Loan Exposure	$ 1,216,864	$ 1,317,846
Percentage of portfolio	5.00%	8.00%
Sweden
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	1
Principal balance	$ 546,319
Total Loan Exposure	$ 551,149
Percentage of portfolio	2.00%
Australia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	4	2
Principal balance	$ 504,668	$ 259,126
Total Loan Exposure	$ 509,885	$ 259,788
Percentage of portfolio	2.00%	1.00%
Canada
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	2	3
Principal balance	$ 68,558	$ 82,185
Total Loan Exposure	$ 68,478	$ 82,262
Percentage of portfolio	0.00%	0.00%
Other Europe
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	3	5
Principal balance	$ 599,016	$ 654,133
Total Loan Exposure	$ 637,561	$ 695,455
Percentage of portfolio	3.00%	4.00%