Loans Receivable - Additional Information (Detail) (USD $)	6 Months Ended					12 Months Ended				6 Months Ended	12 Months Ended	6 Months Ended
	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Loan Origination [Member]	Jun. 30, 2013 Legacy Portfolio [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member]	Jun. 30, 2013 Subordinated Interests in Mortgages [Member]	Jun. 30, 2013 Subordinated Interests in Mortgages [Member] Interest Payments [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member] Interest Payments [Member]	Jun. 30, 2013 Subordinated Interests in Mortgages [Member] Contractual Payments [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member] Contractual Payments [Member]	Jun. 30, 2013 Subordinated Interests in Mortgages [Member] Nonaccrual Status [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member] Nonaccrual Status [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Book Value, net	$ 830,101,000		$ 141,500,000	$ 753,101,000	$ 77,000,000	$ 79,000,000	$ 77,000,000	$ 7,500,000	$ 7,500,000
Unfunded commitments	8,600,000
Commitment termination period	2016-06
Gross book value										10,600,000	17,200,000
Loss reserves on loans						92.00%	100.00%
Net book value of loans						2,000,000
Net book value of loans in maturity default	27,000,000
Number of loans in maturity default	1
Income on impaired subordinate interests in mortgage loans		290,000
Average net book value		3,300,000
Aggregate principal balance												18,100,000	24,700,000
Aggregate net book value												$ 0	$ 2,000,000
Number of days past due for recognizing interest on loans as non accrued												90 days