Loans Receivable - Additional Information (Detail) (USD $)	9 Months Ended				9 Months Ended		12 Months Ended				9 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2013 SecurityLoan	Dec. 31, 2012	Sep. 30, 2013 Loan Origination [Member]	Sep. 30, 2013 CT Legacy Portfolio [Member]	Sep. 30, 2012 CT CDO I [Member]	Sep. 30, 2012 CDO [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member]	Sep. 30, 2013 Subordinated Interests in Mortgages [Member]	Sep. 30, 2013 Subordinated Interests in Mortgages [Member] Interest Payments [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member] Interest Payments [Member]	Sep. 30, 2013 Subordinated Interests in Mortgages [Member] Contractual Payments [Member]	Dec. 31, 2012 Subordinated Interests in Mortgages [Member] Contractual Payments [Member]	Sep. 30, 2013 Subordinated Interests in Mortgages [Member] Nonaccrual Status [Member] MortgageLoan	Dec. 31, 2012 Subordinated Interests in Mortgages [Member] Nonaccrual Status [Member] MortgageLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Book value, net	$ 1,362,891,000	$ 141,500,000	$ 1,285,891,000	$ 77,000,000			$ 79,000,000	$ 77,000,000	$ 7,500,000	$ 7,500,000
Unfunded commitments	96,300,000
Commitments expiration period	5 years
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 loans					404,000	378,000
Average net book value					5,100,000	9,400,000
Aggregate principal balance													18,100,000	24,700,000
Number of subordinate interests in mortgages on nonaccrual status													2	3
Aggregate net book value													$ 0	$ 2,000,000
Number of days past due for recognizing interest on loans as non accrued													90 days