Loans Receivable, Net - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			$ 14,191,200
Unrealized (loss) gain on foreign currency translation	$ (39,961)	$ (2,416)	(44,125)	$ (26,766)
Amortization of fees and other items			40,110	$ 35,955
Ending Balance	14,755,072		14,755,072
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			14,191,200
Loan fundings			3,319,563
Loan repayments and sales proceeds			(2,640,402)
Unrealized (loss) gain on foreign currency translation			(122,490)
Deferred fees and other items			(32,527)
Amortization of fees and other items			39,728
Ending Balance	14,755,072		14,755,072
Deferred Fees/Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			(102,770)
Unrealized (loss) gain on foreign currency translation			1,085
Deferred fees and other items			(32,527)
Amortization of fees and other items			39,728
Ending Balance	(94,484)		(94,484)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			14,293,970
Loan fundings			3,319,563
Loan repayments and sales proceeds			(2,640,402)
Unrealized (loss) gain on foreign currency translation			(123,575)
Ending Balance	$ 14,849,556		$ 14,849,556