Investments - Schedule of Amount of Mortgage Loans (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value $ 572,811 $ 632,507
Percentage of total carrying amount 100.00% 100.00%
Prior to 2005
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 31,473 41,324
Percentage of total carrying amount 5.00% 6.00%
2005
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 25,035 28,111
Percentage of total carrying amount 4.00% 4.00%
2006
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 19,629 24,744
Percentage of total carrying amount 3.00% 4.00%
2007
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 20,471 27,009
Percentage of total carrying amount 4.00% 4.00%
2008
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 23,422 28,051
Percentage of total carrying amount 4.00% 4.00%
2009
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 22,808 37,723
Percentage of total carrying amount 4.00% 6.00%
2010
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 56,579 61,236
Percentage of total carrying amount 10.00% 10.00%
2011
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 94,203 118,459
Percentage of total carrying amount 16.00% 19.00%
2012
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 165,565 184,749
Percentage of total carrying amount 30.00% 29.00%
2013
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value 78,744 81,101
Percentage of total carrying amount 14.00% 14.00%
2014
   
Mortgage Loans on Real Estate [Line Items]    
Mortgage loans, carrying value $ 34,882 $ 0
Percentage of total carrying amount 6.00% 0.00%