Asset-Specific Debt Agreements, Net - Summary of Asset-Specific Financings (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) SecurityLoan	Dec. 31, 2019 USD ($) SecurityLoan
Participating Mortgage Loans [Line Items]
Financing provided, Principal Balance	$ 7,896,863	$ 9,753,059
Collateral Assets [Member]
Participating Mortgage Loans [Line Items]
Financing provided	2023-10	2023-03
Collateral assets, Book Value	$ 499,085	$ 417,820
Collateral assets, Principal Balance	$ 512,794	$ 429,983
Count | SecurityLoan	4	4
LIBOR [Member] | Collateral Assets [Member]
Participating Mortgage Loans [Line Items]
Weighted Average Yield/Cost Rate	4.65%	4.90%
Asset-Specific Financings [Member]
Participating Mortgage Loans [Line Items]
Financing provided	2023-10	2023-03
Guarantee	$ 33,244	$ 97,930
Financing provided, Book Value	391,269	323,504
Financing provided, Principal Balance	$ 399,699	$ 330,879
Count | SecurityLoan	4	4
Asset-Specific Financings [Member] | LIBOR [Member]
Participating Mortgage Loans [Line Items]
Weighted Average Yield/Cost Rate	3.48%	3.42%