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Income Taxes (Income Tax Expense Differences from the Amount Computed by Applying the U.S. Federal Income Tax Rate) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Income Taxes |  |  |
U.S. Federal income tax rate (as a percent) | 21.00% | 35.00% | 35.00%
Reasons for the difference of income tax expense |  |  |
Computed expected tax expense | $ 57,831 | $ 77,643 | $ 69,253
Change in taxes resulting from: |  |  |
Tax-exempt interest income | (3,101) | (4,701) | (3,940)
State tax, net of federal income taxes and tax credit and refunds | 2,673 | 1,697 | 3,287
Resolution of IRS exam |  | (4,985) |
Other investment income | (1,561) | (3,198) | (3,694)
Deferred tax adjustment due to federal tax rate change | (1,618) | (3,168) |
Net investment expense, low income housing investment | 2,518 | 387 |
Other | (90) | 531 | (1,835)
Total income taxes | $ 56,652 | $ 64,206 | $ 63,071

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