Loans Receivable, Net - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			$ 8,692,978
Unrealized gain (loss) on foreign currency translation	$ 20,045	$ (21,321)	27,815	$ (15,343)
Amortization of fees and other items			16,796	$ 20,360
Ending Balance	9,587,457		9,587,457
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			8,692,978
Loan fundings			1,939,614
Loan repayments			(1,117,733)
Unrealized gain (loss) on foreign currency translation			81,030
Deferred fees and other items			(25,228)
Amortization of fees and other items			16,796
Ending Balance	9,587,457		9,587,457
Deferred Fees/Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			(34,240)
Unrealized gain (loss) on foreign currency translation			(177)
Deferred fees and other items			(25,228)
Amortization of fees and other items			16,796
Ending Balance	(42,849)		(42,849)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			8,727,218
Loan fundings			1,939,614
Loan repayments			(1,117,733)
Unrealized gain (loss) on foreign currency translation			81,207
Ending Balance	$ 9,630,306		$ 9,630,306