Loans Receivable, Net - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			$ 8,692,978
Unrealized gain (loss) on foreign currency translation	$ 16,175	$ (10,128)	43,990	$ (25,472)
Amortization of fees and other items			28,887	$ 31,594
Ending Balance	9,637,152		9,637,152
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			8,692,978
Loan fundings			2,789,341
Loan repayments			(1,970,743)
Unrealized gain (loss) on foreign currency translation			135,123
Deferred fees and other items			(38,434)
Amortization of fees and other items			28,887
Ending Balance	9,637,152		9,637,152
Deferred Fees/Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			(34,240)
Unrealized gain (loss) on foreign currency translation			(116)
Deferred fees and other items			(38,434)
Amortization of fees and other items			28,887
Ending Balance	(43,903)		(43,903)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			8,727,218
Loan fundings			2,789,341
Loan repayments			(1,970,743)
Unrealized gain (loss) on foreign currency translation			135,239
Ending Balance	$ 9,681,055		$ 9,681,055