Notes Receivable - Additional Information (Detail) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) SecurityLoan	Dec. 31, 2014 SecurityLoan
Receivables [Abstract]
Number of loans receivable outstanding	5	6
Principal amount of loans subject to delinquent principal or interest | $	$ 9.8
Number of matured loans outstanding	1
Past due on interest payments	more than 90 days
Number of mortgage loans on real estate fully reserved	1
Loan loss reserve | $	$ 4.8