Fair Value Measurements (Details Textual) (USD $)
Jun. 30, 2012
Securities
Dec. 31, 2011
Fair Value Measurements (Textual) [Abstract]    
Fixed maturity securities available for sale, at fair value $ 2,816,250,000 $ 2,682,142,000
Fair Value Measurements (Additional Textual) [Abstract]    
Percentage of carrying value of investments from external pricing services 96.00%  
Percentage of carrying value of investments from brokers 2.00%  
Percentage of carrying value of investments from internal matrices and calculations 2.00%  
Number of securities on which company internally determined the prices 20  
Prices obtained for the number of securities from brokers 7  
Level 3 [Member]
   
Fair Value Measurements (Textual) [Abstract]    
Fixed maturity securities available for sale, at fair value 44,999,000 43,759,000
Fair Value Measurements (Additional Textual) [Abstract]    
Estimated increase in Basis Spread of fixed maturity securities 0.10%  
Reduction in reported fair value $ 200,000