Reverse Mortgage Loans - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($) Loans
Reverse Mortgage Loan Activities [Line Items]
Consolidated mortgage investment	$ 24,500,000	$ 24,500,000
Number of loans | Loans		97
Average age of a mortgage backed securities borrower		94 years
Realizable collateral value of mortgage backed securities	47,100,000	$ 47,100,000
Forecasted housing prices increase rate		2.50%
Forecasted housing prices increase rate, following year and thereafter		2.00%
Internal rate of return		18.58%
Cash payments to reverse mortgagors	5,200,000	$ 5,200,000
Decrease in income	$ 315,000
Reduction in collateral value	1.00%
Maximum [Member]
Reverse Mortgage Loan Activities [Line Items]
Net present value increase (decrease)		$ 769,000
Increase (decrease) in present value of IRR		1.00%
Minimum [Member]
Reverse Mortgage Loan Activities [Line Items]
Percentage of increase decrease in home value		50.00%
Net present value increase (decrease)		$ (752,000)
Increase (decrease) in present value of IRR		(1.00%)
Zero Collateral Value [Member]
Reverse Mortgage Loan Activities [Line Items]
Internal rate of return	17.52%
Decrease in income	$ 685,000
Collateral Value Reduced by One Percent [Member]
Reverse Mortgage Loan Activities [Line Items]
Internal rate of return	18.09%