Loans Receivable, Net - Additional Information (Detail)	3 Months Ended						9 Months Ended				12 Months Ended
	Sep. 30, 2024 USD ($) loan	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2024 USD ($) loan	Sep. 30, 2024 USD ($) security_loan	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) loan	Dec. 31, 2023 USD ($) loan	Dec. 31, 2023 USD ($) security_loan	Dec. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted-average risk rating	3.1						3.1	3.1	3.1		3.1	3.0	3.0
Increase in net CECL reserve	$ 117,100,000
Increase in CECL reserves	134,110,000	$ 155,105,000	$ 235,447,000	$ 99,548,000	$ 27,284,000	$ 10,454,000
Amount charged off	16,989,000	12,537,000	61,013,000				$ 90,539,000
CECL reserve	1,011,059,000	893,938,000	751,370,000	463,423,000	363,875,000	336,591,000	1,011,059,000	$ 1,011,059,000	$ 1,011,059,000	$ 463,423,000	$ 1,011,059,000	$ 576,936,000	$ 576,936,000	$ 326,137,000
Interest and related income	$ 430,092,000			519,342,000			1,382,367,000			1,532,618,000
Number of previously impaired loans resolved | loan	1
Number of loans								149	149			178	178
Loans receivable	$ 21,602,517,000						21,602,517,000	$ 21,602,517,000	$ 21,602,517,000		$ 21,602,517,000	$ 23,787,012,000	$ 23,787,012,000
Number of loan modifications | loan											6
Real estate owned, net	138,725,000						138,725,000	$ 138,725,000	138,725,000		$ 138,725,000	$ 0	0
5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan								20				13
Loans receivable	3,165,612,000						3,165,612,000	$ 3,165,612,000	3,165,612,000		3,165,612,000	$ 1,877,279,000	1,877,279,000
4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan								20				15
Loans receivable	2,843,464,000						2,843,464,000	$ 2,843,464,000	2,843,464,000		$ 2,843,464,000	$ 2,725,930,000	2,725,930,000
Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modifications | loan											2
Aggregate amortized cost basis of loans											$ 347,500,000
Percentage to aggregate loans receivable portfolio											1.60%
Payment Deferral, Loan One
Accounts, Notes, Loans and Financing Receivable [Line Items]
Exit fee percentage											2.00%
Interest rate increase											2.00%
Payment Deferral, Loan Two
Accounts, Notes, Loans and Financing Receivable [Line Items]
Exit fee percentage											3.00%
Interest rate increase											4.00%
Extended Maturity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modifications | loan											4
Aggregate amortized cost basis of loans											$ 457,900,000
Percentage to aggregate loans receivable portfolio											2.10%
Extended Maturity | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modifications | loan											3
Extended Maturity | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan modifications | loan											2
Extended Maturity, Loan One
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extension term											2 years 6 months
Extended Maturity, Loan Two
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extension term											2 years
Increase to loan commitment											$ 34,500,000
Fixed coupon rate											15.00%
Floating rate											2.50%
Extended Maturity, Loan Three
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extension term											7 months
Paid in kind interest rate											5.00%
Extended Maturity, Loan Four
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extension term											10 months
Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in CECL reserves	141,186,000	169,318,000	245,942,000	108,150,000	17,143,000	7,480,000
Amount charged off	16,989,000	12,537,000	61,013,000
CECL reserve	$ 883,577,000	$ 759,380,000	$ 602,599,000	$ 322,551,000	$ 214,401,000	$ 197,258,000	883,577,000	$ 883,577,000	883,577,000	$ 322,551,000	$ 883,577,000	417,670,000	417,670,000	$ 189,778,000
Number of new loans impaired | loan	2
Interest and related income	$ 4,900,000
Number of loans | loan								20
Loans receivable	3,165,612,000						3,165,612,000	$ 3,165,612,000	3,165,612,000		3,165,612,000	1,877,279,000	1,877,279,000
Cash proceeds	24,500,000
Impaired loans | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	3,165,612,000						3,165,612,000	3,165,612,000	3,165,612,000		3,165,612,000	1,877,279,000	1,877,279,000
Impaired loans | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	0						0	$ 0	0		0	$ 0	0
Unfunded Loan Commitment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan								76
Unfunded Loan Commitment | Payment Deferral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded loan commitments	0						0	$ 0	0		0
Unfunded Loan Commitment | Extended Maturity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded loan commitments	61,500,000						61,500,000	$ 61,500,000	61,500,000		61,500,000
Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan								47				54
Loans receivable	8,684,237,000						8,684,237,000	$ 8,684,237,000	8,684,237,000		$ 8,684,237,000	$ 9,253,609,000	9,253,609,000
Number of loan modifications | loan											4
Hospitality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan								17				23
Loans receivable	3,175,423,000						3,175,423,000	$ 3,175,423,000	3,175,423,000		$ 3,175,423,000	$ 4,161,525,000	4,161,525,000
Number of loan modifications | loan											2
Joint Venture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan exposure	294,700,000						294,700,000	294,700,000	294,700,000		$ 294,700,000	612,900,000	612,900,000
Real estate owned, net	$ 32,200,000						$ 32,200,000	$ 32,200,000	$ 32,200,000		$ 32,200,000	$ 0	$ 0