Reverse Mortgage Loans - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2016 USD ($) Loans
Reverse Mortgage Loan Activities [Line Items]
Consolidated mortgage investment	$ 25,300,000	$ 25,300,000
Number of loans | Loans		88
Average age of a mortgage backed securities borrower		94 years
Realizable collateral value of mortgage backed securities	45,500,000	$ 45,500,000
Forecasted housing prices increase rate		2.50%
Forecasted housing prices increase rate, following year and thereafter		2.00%
Internal rate of return		19.62%
Cash payments to reverse mortgages	5,900,000	$ 5,900,000
Decrease in income	$ 339,000
Reduction in collateral value	1.00%
Minimum [Member]
Reverse Mortgage Loan Activities [Line Items]
Percentage of increase decrease in home value		50.00%
Net present value increase (decrease)		$ (1,068,000)
Increase (decrease) in present value of IRR		(1.00%)
Maximum [Member]
Reverse Mortgage Loan Activities [Line Items]
Net present value increase (decrease)		$ 1,102,000
Increase (decrease) in present value of IRR		1.00%
Zero Collateral Value [Member]
Reverse Mortgage Loan Activities [Line Items]
Internal rate of return	18.81%
Decrease in income	$ 741,000
Collateral Value Reduced by One Percent [Member]
Reverse Mortgage Loan Activities [Line Items]
Internal rate of return	19.25%