Loans Receivable, Net - Principal Balance and Net Book Value of Loans Receivable Based on Internal Risk Ratings (Detail) $ in Thousands	Sep. 30, 2022 USD ($) SecurityLoan	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) SecurityLoan	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	205			188
Net Book Value	$ 24,423,133			$ 22,003,017
CECL reserve	(144,431)	$ (133,024)	$ (122,221)	(124,679)	$ (130,388)	$ (128,945)	$ (172,100)	$ (173,549)
Loans receivable, net	24,278,702			21,878,338
Total Loan Exposure	26,136,006			23,669,111
Total loan exposure including senior interests	$ 1,600,000			1,500,000
2018 Single Asset Securitization
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loan amount, securitized				$ 379,300
1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	12			8
Net Book Value	$ 1,059,274			$ 642,776
Total Loan Exposure	$ 1,081,961			$ 645,854
2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	42			28
Net Book Value	$ 6,323,262			$ 5,200,533
Total Loan Exposure	$ 7,008,246			$ 5,515,250
3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	137			141
Net Book Value	$ 14,070,849			$ 13,604,027
Total Loan Exposure	$ 15,072,206			$ 14,944,045
4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	13			10
Net Book Value	$ 2,684,939			$ 2,270,872
Total Loan Exposure	$ 2,687,284			$ 2,277,653
5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	1			1
Net Book Value	$ 284,809			$ 284,809
Total Loan Exposure	$ 286,309			$ 286,309