Schedule of Fixed Maturity and Equity Security Investments Available for Sale with Unrealized Losses (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2012
Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value $ 25,726 $ 155,090
Less Than 12 Months, Unrealized Losses 490 7,394
12 Months or Fair Value 119,862 149,525
12 Months or Longer, Unrealized Losses 14,365 23,946
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 145,588 304,615
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 14,855 31,340
U.S. Treasury securities and obligations of U.S. Government
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 1,362  
Less Than 12 Months, Unrealized Losses 18  
12 Months or Fair Value 784 959
12 Months or Longer, Unrealized Losses 9 12
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 2,146 959
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 27 12
Federal agency issued residential mortgage-backed securities
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 10 [1] 649 [1]
12 Months or Fair Value 293 [1] 294 [1]
12 Months or Longer, Unrealized Losses 1 [1] 2 [1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 303 [1] 943 [1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 1 [1] 2 [1]
US treasury securities
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 1,372 649
Less Than 12 Months, Unrealized Losses 18  
12 Months or Fair Value 1,077 1,253
12 Months or Longer, Unrealized Losses 10 14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 2,449 1,902
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 28 14
Industrial
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 8,462 25,455
Less Than 12 Months, Unrealized Losses 430 860
12 Months or Fair Value 2,825  
12 Months or Longer, Unrealized Losses 1,319  
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 11,287 25,455
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 1,749 860
Energy
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 1,980  
Less Than 12 Months, Unrealized Losses 17  
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 1,980  
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 17  
Communications and technology
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value   7,239
Less Than 12 Months, Unrealized Losses   156
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total   7,239
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses   156
Financial
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 1,502 51,273
Less Than 12 Months, Unrealized Losses 1 2,107
12 Months or Fair Value 15,053 16,402
12 Months or Longer, Unrealized Losses 1,906 3,783
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 16,555 67,675
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 1,907 5,890
Consumer
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 7,336 11,765
Less Than 12 Months, Unrealized Losses 14 119
12 Months or Fair Value   3,689
12 Months or Longer, Unrealized Losses   144
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 7,336 15,454
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 14 263
Public utilities
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 1,995 4,710
Less Than 12 Months, Unrealized Losses 5 344
12 Months or Fair Value 1,240 11,152
12 Months or Longer, Unrealized Losses 350 1,022
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 3,235 15,862
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 355 1,366
Corporate obligations
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 21,275 100,442
Less Than 12 Months, Unrealized Losses 467 3,586
12 Months or Fair Value 19,118 31,243
12 Months or Longer, Unrealized Losses 3,575 4,949
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 40,393 131,685
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 4,042 8,535
Corporate private-labeled residential mortgage-backed securities
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value   41,734
Less Than 12 Months, Unrealized Losses   2,668
12 Months or Fair Value 52,908 61,864
12 Months or Longer, Unrealized Losses 1,575 9,952
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 52,908 103,598
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 1,575 12,620
Municipal securities
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 3,079  
Less Than 12 Months, Unrealized Losses 5  
12 Months or Fair Value   3,909
12 Months or Longer, Unrealized Losses   61
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 3,079 3,909
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 5 61
Other
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value   9,257
Less Than 12 Months, Unrealized Losses   921
12 Months or Fair Value 43,087 47,146
12 Months or Longer, Unrealized Losses 8,973 8,314
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 43,087 56,403
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 8,973 9,235
Redeemable preferred stocks
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value   2,939
Less Than 12 Months, Unrealized Losses   115
12 Months or Fair Value 2,521 3,056
12 Months or Longer, Unrealized Losses 126 625
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 2,521 5,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 126 740
Fixed maturity securities available for sale
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value 25,726 155,021
Less Than 12 Months, Unrealized Losses 490 7,290
12 Months or Fair Value 118,711 148,471
12 Months or Longer, Unrealized Losses 14,259 23,915
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 144,437 303,492
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses 14,749 31,205
Equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Fair Value   69
Less Than 12 Months, Unrealized Losses   104
12 Months or Fair Value 1,151 1,054
12 Months or Longer, Unrealized Losses 106 31
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total 1,151 1,123
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses $ 106 $ 135
[1] Federal agency securities are not backed by the full faith and credit of the U.S. Government.