v2.4.0.8
Investments (Details 4) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2013
Dec. 31, 2012
Investments in LPs/LLCs [Member]
    
Investments held in an unrealized loss position    
Other Investments, Continuous Unrealized Loss Position, Fair Value $ 4,972 $ 9,474
Other Investments, Continuous Unrealized Loss Position, Aggregate Losses (325) (851)
Other investments, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 3,906 8,697
Other Investments, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses (294) (688)
Other Investments, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,066 777
Other Investments, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses (31) (163)
U.S. Treasury obligations [Member]
    
Investments held in an unrealized loss position    
Fair Value 54,610 4,073
Unrealized Loss (1,383) (51)
Less than 12 months, Fair Value 54,610 4,073
Less than 12 months, Unrealized Loss (1,383) (51)
More than 12 months, Fair Value 0 0
More than 12 months, Unrealized Loss 0 0
US Government-sponsored Enterprises Debt Securities [Member]
    
Investments held in an unrealized loss position    
Fair Value 5,579  
Unrealized Loss (293)  
Less than 12 months, Fair Value 5,579  
Less than 12 months, Unrealized Loss (293)  
More than 12 months, Fair Value 0  
More than 12 months, Unrealized Loss 0  
State and municipal bonds [Member]
    
Investments held in an unrealized loss position    
Fair Value 210,096 11,234
Unrealized Loss (7,113) (94)
Less than 12 months, Fair Value 208,105 9,232
Less than 12 months, Unrealized Loss (7,089) (65)
More than 12 months, Fair Value 1,991 2,002
More than 12 months, Unrealized Loss (24) (29)
Corporate debt [Member]
    
Investments held in an unrealized loss position    
Fair Value 423,388 90,154
Unrealized Loss (16,314) (1,543)
Less than 12 months, Fair Value 416,240 81,878
Less than 12 months, Unrealized Loss (15,961) (1,377)
More than 12 months, Fair Value 7,148 8,276
More than 12 months, Unrealized Loss (353) (166)
Residential mortgage-backed securities [Member]
    
Investments held in an unrealized loss position    
Fair Value 75,441 10,721
Unrealized Loss (1,993) (210)
Less than 12 months, Fair Value 74,789 10,029
Less than 12 months, Unrealized Loss (1,990) (205)
More than 12 months, Fair Value 652 692
More than 12 months, Unrealized Loss (3) (5)
Agency commercial mortgage-backed securities [Member]
    
Investments held in an unrealized loss position    
Fair Value 5,252 1,643
Unrealized Loss (69) (25)
Less than 12 months, Fair Value 4,765 498
Less than 12 months, Unrealized Loss (59) (2)
More than 12 months, Fair Value 487 1,145
More than 12 months, Unrealized Loss (10) (23)
Other commercial mortgage-backed securities [Member]
    
Investments held in an unrealized loss position    
Fair Value 13,309 2,100
Unrealized Loss (260) (5)
Less than 12 months, Fair Value 13,309 1,103
Less than 12 months, Unrealized Loss (260) (1)
More than 12 months, Fair Value 0 997
More than 12 months, Unrealized Loss 0 (4)
Other asset-backed securities [Member]
    
Investments held in an unrealized loss position    
Fair Value 26,728 10,746
Unrealized Loss (393) (601)
Less than 12 months, Fair Value 23,397 7,707
Less than 12 months, Unrealized Loss (158) (20)
More than 12 months, Fair Value 3,331 3,039
More than 12 months, Unrealized Loss (235) (581)
Debt Securities [Member]
    
Investments held in an unrealized loss position    
Fair Value 814,403 130,671
Unrealized Loss (27,818) (2,529)
Less than 12 months, Fair Value 800,794 114,520
Less than 12 months, Unrealized Loss (27,193) (1,721)
More than 12 months, Fair Value 13,609 16,151
More than 12 months, Unrealized Loss $ (625) $ (808)