Fair Values - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($) SecurityLoan	Sep. 30, 2015 USD ($) SecurityLoan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Book value of securities | $		$ 10.2
Loans receivable | $	$ 19.0
Number of loans		0
Aggregate book value of equity investments and other receivables | $		$ 2.9
Hotel [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of loans	1
Discount rate	7.00%
Fair value of a 100 bp discount rate increase	0.30%
Office [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of loans	1
Discount rate	15.00%
Fair value of a 100 bp discount rate increase	1.10%