Loans Receivable - Activity Relating to Loans Receivable Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			$ 9,077,007
Unrealized (loss) gain on foreign currency translation	$ (10,128)	$ (23,148)	(25,472)	$ (27,484)
Amortization of fees and other items			31,594	$ 25,489
Ending Balance	8,347,712		8,347,712
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			9,077,007
Loan fundings			2,300,636
Loan repayments and sales			(2,942,705)
Unrealized (loss) gain on foreign currency translation			83,432
Deferred fees and other items			(35,388)
Amortization of fees and other items			31,594
Ending Balance	8,347,712		8,347,712
Deferred Fees/Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			(31,354)
Unrealized (loss) gain on foreign currency translation			1,181
Deferred fees and other items			(35,388)
Amortization of fees and other items			31,594
Ending Balance	(33,967)		(33,967)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			9,108,361
Loan fundings			2,300,636
Loan repayments and sales			(2,942,705)
Unrealized (loss) gain on foreign currency translation			84,613
Ending Balance	$ 8,381,679		$ 8,381,679