Loans Receivable, Net - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Beginning Balance Principal Balance	$ 16,277,343	$ 14,293,970
Loan fundings Principal Balance	1,896,276	6,890,249
Loan Repayments and sales proceeds principal balance	(1,862,955)	(4,974,881)
Unrealized gain (loss) on foreign currency translation Principal Balance	342,160	68,005
Loans Receivable, Ending Balance Principal Balance	16,652,824	16,277,343	$ 14,293,970
Loans Receivable, Beginning Balance Deferred Fees/ Other Items	(112,542)	(102,770)
Unrealized gain (loss) on foreign currency translation Deferred Fees/ Other Items	(1,900)	(629)
Amortization of fees and other items Deferred Fees/ Other Items	56,279	57,415
Loans Receivable, Ending Balance Deferred Fees/ Other Items	(80,109)	(112,542)	(102,770)
Balance at January 1,	16,164,801	14,191,200	10,056,732
Loan fundings Net Book Value	1,896,276	6,890,249
Loan repayments and sales proceeds	(1,862,955)	(4,974,881)	(3,035,383)
Unrealized gain (loss) on foreign currency translation Net Book Value	340,260	67,376
Deferred fees and other items	(21,946)	(66,558)
Amortization of fees and other items Net Book Value	56,279	57,415
Balance at December 31,	16,572,715	16,164,801	14,191,200
CECL reserve	(173,549)	0
Net book value of restructured loan	$ 16,399,166	$ 16,164,801	$ 14,191,200