Loans Receivable - Activity Relating to Loans Receivable (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014			$ 4,428,500
Unrealized gain (loss) on foreign currency translation	$ 15,732	$ 1,894	(4,336)	$ 1,930
June 30, 2015	10,131,323		10,131,323
Principal Balance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014			4,462,897
Loan purchases and fundings			6,430,243
Loan repayments and sales			723,922
Unrealized gain (loss) on foreign currency translation			391
June 30, 2015	10,169,609		10,169,609
Deferred Fees/Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014			(34,397)
Unrealized gain (loss) on foreign currency translation			(286)
Deferred fees and other items			(16,373)
Amortization of fees and other items			12,198
June 30, 2015	(38,286)		(38,286)
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014			4,428,500
Loan purchases and fundings			6,430,243
Loan repayments and sales			723,922
Unrealized gain (loss) on foreign currency translation			677
Deferred fees and other items			16,373
Amortization of fees and other items			(12,198)
June 30, 2015	$ 10,131,323		$ 10,131,323