Loans Receivable - Activity Relating to Loans Receivable (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan fundings	$ 3,067,263	$ 2,327,914	$ 26
Unrealized loss on foreign currency translation	15,822	(798)
Deferred origination fees and expenses	(35,449)	(25,402)
Amortization of deferred fees and expenses	(19,785)	(6,290)	(566)
Reclassification to other assets	(27,000)
Net Book Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2013	2,047,223
Loan fundings	3,067,263
Loan repayments and sales	(591,246)
Unrealized loss on foreign currency translation	(52,076)
Deferred origination fees and expenses	(35,449)
Amortization of deferred fees and expenses	19,785
Reclassification to other assets	(27,000)
December 31, 2014	4,428,500
Deferred Fees and Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2013	(30,004)
Unrealized loss on foreign currency translation	725
Deferred origination fees and expenses	(35,449)
Amortization of deferred fees and expenses	19,785
Realized loan losses	10,546
December 31, 2014	(34,397)
Principal Balance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
December 31, 2013	2,077,227
Loan fundings	3,067,263
Loan repayments and sales	(591,246)
Unrealized loss on foreign currency translation	(52,801)
Realized loan losses	(10,546)
Reclassification to other assets	(27,000)
December 31, 2014	$ 4,462,897