Loans Receivable, Net - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans receivable, Beginning Balance Principal Balance	$ 16,652,824
Loan fundings Principal Balance	1,405,119
Loan repayments and sales Principal balance	(798,155)
Unrealized (loss) gain on foreign currency translation Principal Balance	(116,686)
Loans receivable, Ending Balance Principal Balance	17,143,102
Loans receivable, Beginning Balance Deferred Fees/ Other Items	(80,109)
Unrealized gain (loss) on foreign currency translation Deferred Fees/ Other Items	524
Deferred fees and other items Deferred Fees/ Other Items	(17,475)
Amortization of fees and other items Deferred Fees/ Other Items	14,060
Loans receivable, Ending Balance Deferred Fees/ Other Items	(83,000)
Loans receivable, Beginning Balance Net Book Value	16,572,715
Loan fundings Net Book Value	1,405,119
Loan repayments and sales proceeds	(798,155)
Unrealized gain (loss) on foreign currency translation Net Book Value	(116,162)
Deferred fees and other items Net Book Value	(17,475)
Amortization of fees and other items Net Book Value	14,060
Loans receivable, Ending Balance Net Book Value	17,060,102
CECL reserve	(172,100)	$ (173,549)	$ (112,694)	$ 0
Net book value of restructured loan	$ 16,888,002	$ 16,399,166