Loans Receivable, Net - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			$ 14,191,200
Unrealized (loss) gain on foreign currency translation	$ (9,578)	$ (35,088)	(4,164)	$ (24,350)
Amortization of fees and other items			28,511	$ 24,161
Ending Balance	14,280,919		14,280,919
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			14,191,200
Loan fundings			1,922,219
Loan repayments			(1,833,414)
Unrealized (loss) gain on foreign currency translation			(9,621)
Deferred fees and other items			(17,721)
Amortization of fees and other items			28,256
Ending Balance	14,280,919		14,280,919
Deferred Fees/Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			(102,770)
Unrealized (loss) gain on foreign currency translation			204
Deferred fees and other items			(17,721)
Amortization of fees and other items			28,256
Ending Balance	(92,031)		(92,031)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			14,293,970
Loan fundings			1,922,219
Loan repayments			(1,833,414)
Unrealized (loss) gain on foreign currency translation			(9,825)
Ending Balance	$ 14,372,950		$ 14,372,950