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Summary of Significant Accounting Policies (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Adjustments to the financial statement Consolidated Statement of Operations |  |  |  |  |  |  |  |  |  |  |
Underwriting and certain other operating costs |  |  |  |  |  |  |  |  | $ 18,450 | $ 22,404 | $ 6,409
Income before income taxes | 12,674 | 9,003 | 4,033 | 11,433 | 9,517 | 5,518 | 4,832 | 7,490 | 37,143 | 27,357 | 44,222
Income tax expense |  |  |  |  |  |  |  |  | 7,790 | 3,176 | 9,702
Net income | 9,226 | 7,121 | 3,445 | 9,561 | 8,073 | 4,884 | 4,594 | 6,630 | 29,353 | 24,181 | 34,520
Basic earnings per share | $ 0.51 | $ 0.39 | $ 0.19 | $ 0.53 | $ 0.45 | $ 0.27 | $ 0.25 | $ 0.36 | $ 1.62 | $ 1.32 | $ 1.85
As Reported [Member] |  |  |  |  |  |  |  |  |  |  |
Adjustments to the financial statement Consolidated Statement of Operations |  |  |  |  |  |  |  |  |  |  |
Underwriting and certain other operating costs |  |  |  |  |  |  |  |  |  | 22,490 | 6,277
Income before income taxes |  |  |  |  | 9,494 | 5,498 | 4,793 | 7,486 |  | 27,271 | 44,354
Income tax expense |  |  |  |  |  |  |  |  |  | 3,146 | 9,748
Net income |  |  |  |  | 8,058 | 4,871 | 4,569 | 6,627 |  | 24,125 | 34,606
Basic earnings per share |  |  |  |  |  |  |  |  |  |  | $ 1.86
Adjustment [Member] |  |  |  |  |  |  |  |  |  |  |
Adjustments to the financial statement Consolidated Statement of Operations |  |  |  |  |  |  |  |  |  |  |
Underwriting and certain other operating costs |  |  |  |  |  |  |  |  |  | (86) | 132
Income before income taxes |  |  |  |  |  |  |  |  |  | 86 | (132)
Income tax expense |  |  |  |  |  |  |  |  |  | 30 | (46)
Net income |  |  |  |  |  |  |  |  |  | 56 | (86)
Basic earnings per share |  |  |  |  |  |  |  |  |  |  | $ (0.01)
As Adjusted [Member] |  |  |  |  |  |  |  |  |  |  |
Adjustments to the financial statement Consolidated Statement of Operations |  |  |  |  |  |  |  |  |  |  |
Underwriting and certain other operating costs |  |  |  |  |  |  |  |  |  | 22,404 | 6,409
Income before income taxes |  |  |  |  |  |  |  |  |  | 27,357 | 44,222
Income tax expense |  |  |  |  |  |  |  |  |  | 3,176 | 9,702
Net income |  |  |  |  |  |  |  |  |  | $ 24,181 | $ 34,520
Basic earnings per share |  |  |  |  |  |  |  |  |  |  | $ 1.85

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