Investments - Additional Information (Detail) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2011
Investment Securities [Line Items]          
Decline in fair value as a percentage of amortized cost     10.00%    
Percentage of concentration of mortgage loans by state 5.00%   5.00%   5.00%
Time frame for initial default rates assumed to remain constant     24 months    
Number of fixed maturities and equity securities below cost 41   41   85
Allowance for potential future losses $ (2,442,000)   $ (2,442,000)   $ (2,849,000)
Percentage of invested assets in commercial mortgage loans 15.00%   15.00%   17.00%
Average loan to value ratio for overall portfolio 44.00%   44.00%   46.00%
Loans refinanced 4,500,000 0 13,100,000 9,700,000  
Maximum period of commits to fund commercial mortgage loans 120 days   120 days    
Construction to permanent loan 2,800,000   2,800,000    
Construction to permanent loan disbursed $ 2,500,000   $ 2,500,000    
Less than one year
         
Investment Securities [Line Items]          
Number of fixed maturities and equity securities below cost 12   12   46
One year or more and less than three years
         
Investment Securities [Line Items]          
Number of fixed maturities and equity securities below cost 5   5   10
Three years or more
         
Investment Securities [Line Items]          
Number of fixed maturities and equity securities below cost 24   24   29
Maximum
         
Investment Securities [Line Items]          
Percentage of concentration of mortgage loans by state 80.00%   80.00%    
Minimum
         
Investment Securities [Line Items]          
Percentage of concentration of mortgage loans by state 10.00%   10.00%