Loans Receivable - Activity Relating to Loans Receivable (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unrealized loss on foreign currency translation	$ (16,732)	$ 36
Deferred origination fees and expenses	(6,078)	(7,121)
Amortization of deferred fees and expenses	(5,717)	(3,470)
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014	4,428,500
Loan fundings	903,152
Loan repayments and sales	(333,113)
Unrealized loss on foreign currency translation	(54,795)
Deferred origination fees and expenses	(6,078)
Amortization of deferred fees and expenses	5,717
March 31, 2015	4,943,383
Deferred Fees and Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014	(34,397)
Unrealized loss on foreign currency translation	673
Deferred origination fees and expenses	(6,078)
Amortization of deferred fees and expenses	5,717
March 31, 2015	(34,085)
Principal Balance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2014	4,462,897
Loan fundings	903,152
Loan repayments and sales	(333,113)
Unrealized loss on foreign currency translation	(55,468)
March 31, 2015	$ 4,977,468