Reverse Mortgage Loans - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015 Loans
Reverse Mortgage Loan Activities [Line Items]
Consolidated mortgage investment	$ 27,000,000
Number of loans	108
Average age of a mortgage backed securities borrower	93 years
Realizable collateral value of mortgage backed securities	50,300,000
Forecasted housing prices increase rate	2.50%
Forecasted housing prices increase rate, following year and thereafter	2.00%
Internal rate of return	17.48%
Cash payments to reverse mortgagors	6,400,000
Decrease in income	286,000
Reduction in collateral value	1.00%
Maximum [Member]
Reverse Mortgage Loan Activities [Line Items]
Net present value increase or decrease	570,000
Change in present value of IRR	1.00%
Minimum [Member]
Reverse Mortgage Loan Activities [Line Items]
Net present value increase or decrease	561,000
Change in present value of IRR	1.00%
Zero Collateral Value [Member]
Reverse Mortgage Loan Activities [Line Items]
Internal rate of return	16.20%
Decrease in income	$ 623,000
Collateral Value Reduced by One Percent [Member]
Reverse Mortgage Loan Activities [Line Items]
Internal rate of return	16.90%