Loans Receivable, Net - Principal Balance and Net Book Value of Loans Receivable Based on Internal Risk Ratings (Detail) $ in Thousands	Mar. 31, 2022 USD ($) SecurityLoan	Dec. 31, 2021 USD ($) SecurityLoan	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	203	188
Principal balance	$ 23,708,990	$ 22,003,017
CECL reserve	(122,221)	(124,679)	$ (172,100)	$ (173,549)
Loans receivable, net	23,586,769	21,878,338
Total Loan Exposure	25,627,588	23,669,111
Total loan exposure including senior interests	$ 1,800,000	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	5	8
Principal balance	$ 426,984	$ 642,776
Total Loan Exposure	$ 429,779	$ 645,854
2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	39	28
Principal balance	$ 5,982,543	$ 5,200,533
Total Loan Exposure	$ 6,456,584	$ 5,515,250
3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	148	141
Principal balance	$ 14,827,128	$ 13,604,027
Total Loan Exposure	$ 16,261,775	$ 14,944,045
4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	10	10
Principal balance	$ 2,187,526	$ 2,270,872
Total Loan Exposure	$ 2,193,141	$ 2,277,653
5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | SecurityLoan	1	1
Principal balance	$ 284,809	$ 284,809
Total Loan Exposure	$ 286,309	$ 286,309