v2.4.0.6
Segment Reporting Disclosures (Company's Segment Disclosures) (Details) (USD $)
 3 Months Ended 9 Months Ended 12 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
segment
Sep. 30, 2011
Dec. 31, 2012
Accounting Standards Update 2010-26 [Member]
Sep. 30, 2012
Excess And Surplus Lines [Member]
Sep. 30, 2011
Excess And Surplus Lines [Member]
Sep. 30, 2012
Excess And Surplus Lines [Member]
Sep. 30, 2011
Excess And Surplus Lines [Member]
Sep. 30, 2012
Specialty Admitted [Member]
Sep. 30, 2011
Specialty Admitted [Member]
Sep. 30, 2012
Specialty Admitted [Member]
Sep. 30, 2011
Specialty Admitted [Member]
Sep. 30, 2012
London Insurance Market [Member]
Sep. 30, 2011
London Insurance Market [Member]
Sep. 30, 2012
London Insurance Market [Member]
Sep. 30, 2011
London Insurance Market [Member]
Sep. 30, 2012
Other Insurance (Discontinued Lines) [Member]
Sep. 30, 2011
Other Insurance (Discontinued Lines) [Member]
Sep. 30, 2012
Other Insurance (Discontinued Lines) [Member]
Sep. 30, 2011
Other Insurance (Discontinued Lines) [Member]
Sep. 30, 2012
Investing [Member]
Sep. 30, 2011
Investing [Member]
Sep. 30, 2012
Investing [Member]
Sep. 30, 2011
Investing [Member]
Segment Reporting Information [Line Items]                                                  
Number of segments of the specialty insurance marketplace in which the Company operates     3                                            
Gross premium volume $ 610,833,000 $ 584,635,000 $ 1,906,373,000 $ 1,772,611,000   $ 253,014,000 $ 236,639,000 $ 705,849,000 $ 663,989,000 $ 167,747,000 $ 153,753,000 $ 496,019,000 $ 431,604,000 $ 190,071,000 $ 194,210,000 $ 704,511,000 $ 676,893,000 $ 1,000 $ 33,000 $ (6,000) $ 125,000 $ 0 $ 0 $ 0 $ 0
Net written premiums 539,624,000 524,678,000 1,687,404,000 1,574,378,000   211,538,000 200,658,000 597,742,000 570,243,000 157,894,000 147,169,000 467,722,000 410,700,000 170,193,000 176,829,000 621,947,000 593,440,000 (1,000) 22,000 (7,000) (5,000) 0 0 0 0
Earned premiums 530,537,000 509,203,000 1,573,189,000 1,462,515,000   195,478,000 189,695,000 584,524,000 557,958,000 153,009,000 136,783,000 431,179,000 390,623,000 182,052,000 182,710,000 557,493,000 513,947,000 (2,000) 15,000 (7,000) (13,000) 0 0 0 0
Losses and loss adjustment expenses, current accident year (372,740,000) (405,575,000) (1,073,238,000) (1,177,848,000)   (134,504,000) (147,992,000) (390,254,000) (413,049,000) (116,044,000) (112,607,000) (310,115,000) (285,401,000) (122,192,000) (144,976,000) (372,869,000) (479,398,000) 0 0 0 0 0 0 0 0
Losses and loss adjustment expenses, prior accident years 69,281,000 98,943,000 260,164,000 250,205,000   51,310,000 60,475,000 132,583,000 169,916,000 11,504,000 5,973,000 27,747,000 7,942,000 32,744,000 34,721,000 118,994,000 69,960,000 (26,277,000) (2,226,000) (19,160,000) 2,387,000 0 0 0 0
Prospective adoption of ASU 2010-26 (6,534,000) [1]   (41,093,000) [2]     (2,125,000) [1]   (16,652,000) [2]   (2,600,000) [1]   (12,863,000) [2]   (1,809,000) [1]   (11,578,000) [2]   0 [1]   0 [2]   0 [1]   0 [2]  
All other expenses (225,307,000)   (654,229,000)     (88,093,000)   (255,295,000)   (60,008,000)   (171,111,000)   (76,820,000)   (226,770,000)   (386,000)   (1,053,000)   0   0  
Underwriting, acquisition and insurance expenses (231,841,000) (202,316,000) (695,322,000) (601,511,000)     (81,563,000)   (250,415,000)   (51,695,000)   (148,957,000)   (69,731,000)   (202,291,000)   673,000   152,000   0   0
Underwriting profit (loss) (4,763,000) 255,000 64,793,000 (66,639,000)   22,066,000 20,615,000 54,906,000 64,410,000 (14,139,000) (21,546,000) (35,163,000) (35,793,000) 13,975,000 2,724,000 65,270,000 (97,782,000) (26,665,000) (1,538,000) (20,220,000) 2,526,000 0 0 0 0
Net investment income 64,438,000 62,199,000 207,834,000 196,551,000   0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 64,438,000 62,199,000 207,834,000 196,551,000
Net realized investment gains 5,231,000 12,839,000 25,356,000 25,423,000   0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5,231,000 12,839,000 25,356,000 25,423,000
Other revenues (insurance) 11,759,000 10,061,000 40,818,000 31,622,000   0 0 0 0 11,536,000 10,061,000 36,065,000 31,622,000 223,000 0 4,753,000 0 0 0 0 0 0 0 0 0
Other expenses (insurance) (13,151,000) (2,999,000) (37,906,000) (27,374,000)   0 0 0 0 (12,181,000) (3,046,000) (35,184,000) (27,374,000) (970,000) 47,000 (2,722,000) 0 0 0 0 0 0 0 0 0
Segment profit (loss) 63,514,000 82,355,000 300,895,000 159,583,000   22,066,000 20,615,000 54,906,000 64,410,000 (14,784,000) (14,531,000) (34,282,000) (31,545,000) 13,228,000 2,771,000 67,301,000 (97,782,000) (26,665,000) (1,538,000) (20,220,000) 2,526,000 69,669,000 75,038,000 233,190,000 221,974,000
Other revenues (non-insurance) 153,810,000 81,786,000 344,960,000 228,739,000                                          
Other expenses (non-insurance) (132,188,000) (67,303,000) (305,556,000) (190,896,000)                                          
Amortization of intangible assets (7,959,000) (6,023,000) (25,078,000) (17,586,000)                                          
Interest expense (24,692,000) (23,656,000) (69,068,000) (64,516,000)                                          
Income before income taxes 52,485,000 67,159,000 246,153,000 115,324,000                                          
U.S. GAAP combined ratio 101.00% [3] 100.00% [3] 96.00% [3] 105.00% [3]   89.00% [3] 89.00% [3] 91.00% [3] 88.00% [3] 109.00% [3] 116.00% [3] 108.00% [3] 109.00% [3] 92.00% [3] 99.00% [3] 88.00% [3] 119.00% [3]                
U.S. GAAP combined ratio - not meaniningful                                   NM [3],[4] NM [3],[4] NM [3],[4] NM [3],[4]        
Costs expected to be recognized in income, effect of adoption         $ 43,000,000                                        
[1] Effective January 1, 2012, the Company prospectively adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2010-26, Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts. At December 31, 2011, deferred policy acquisition costs included approximately $43 million of costs that no longer met the criteria for deferral as of January 1, 2012 and will be recognized into income primarily over the first nine months of 2012, consistent with policy terms. The quarter ended September 30, 2012 included $6.5 million of underwriting, acquisition and insurance expenses that were deferred as of December 31, 2011 and no longer met the criteria for deferral as of January 1, 2012.
[2] Effective January 1, 2012, the Company prospectively adopted FASB ASU No. 2010-26, Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts. At December 31, 2011, deferred policy acquisition costs included approximately $43 million of costs that no longer met the criteria for deferral as of January 1, 2012 and will be recognized into income primarily over the first nine months of 2012, consistent with policy terms. The nine months ended September 30, 2012 included $41.1 million of underwriting, acquisition and insurance expenses that were deferred as of December 31, 2011 and no longer met the criteria for deferral as of January 1, 2012.
[3] The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.
[4] NM – Ratio is not meaningful.