Loans Receivable - Principal Balance and Net Book Value of Loans Receivable Based on Internal Risk Ratings (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014 SecurityLoan	Dec. 31, 2013 SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net book value	$ 3,488,179	$ 2,047,223
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	48	31
Principal Balance	3,514,032	2,076,411
Net book value	3,488,179	2,047,223
Loans Receivable [Member] | Risk Rating 1-3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net book value	3,488,179	2,020,223
Loans Receivable [Member] | Risk Rating 6-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net book value		27,000
Subordinate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	2	5
Principal Balance	207,457	264,898
Net book value	202,781	246,894
Subordinate Loans [Member] | Risk Rating 1-3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	2	3
Principal Balance	207,457	227,350
Net book value	202,781	219,894
Subordinate Loans [Member] | Risk Rating 6-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans		2
Principal Balance		37,548
Net book value		27,000
Senior Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	46	26
Principal Balance	3,306,575	1,811,513
Net book value	3,285,398	1,800,329
Senior Loans [Member] | Risk Rating 1-3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans	46	26
Principal Balance	3,306,575	1,811,513
Net book value	$ 3,285,398	$ 1,800,329