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Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Income Taxes |  |  |
Income tax expense differences from the amount computed by applying the U.S. Federal income tax rate to income before income taxes (as a percent) | 35.00% | 35.00% | 35.00%
Reasons for the difference of income tax expense |  |  |
Computed expected tax expense | $ 55,634 | $ 66,941 | $ 70,355
Change in taxes resulting from: |  |  |
Tax-exempt interest income | (4,381) | (3,682) | (2,813)
State tax, net of federal income taxes and tax credit | 1,446 | 3,302 | 2,594
Tax refunds |  |  | (2,143)
Litigation expense |  |  | 5,375
Other investment income | (2,691) | (3,083) | (3,172)
Other | 557 | 600 | 761
Total income taxes | $ 50,565 | $ 64,078 | $ 70,957

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