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Income Taxes Income Taxes (Notes) | 9 Months Ended
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Sep. 30, 2018
Income Tax Disclosure [Abstract] |
Income Tax Disclosure [Text Block] | INCOME TAXES The following table summarizes the significant differences in income tax expense based on the differences between our effective tax rate and the federal statutory rates (21 percent in 2018 and 35 percent in 2017) for three and nine months ended September 30 (dollars in thousands):
| Three months ended September 30, |  | Nine months ended September 30,
| 2018 |  | 2017 |  | 2018 |  | 2017
Federal income taxes at statutory rates | $ | 2,452 |  | 21.0 | % |  | $ | 3,364 |  | 35.0 | % |  | $ | 22,721 |  | 21.0 | % |  | $ | 48,953 |  | 35.0 | %
Increase (decrease) in tax resulting from: |  |  |  |  |  |  |  |  |  |  |
Tax effect of regulatory treatment of utility plant differences | (1,521 | ) | (13.0 | ) |  | 742 |  | 7.7 |  |  | (4,519 | ) | (4.2 | ) |  | 2,244 |  | 1.6 |
State income tax expense | (319 | ) | (2.7 | ) |  | (301 | ) | (3.1 | ) |  | 694 |  | 0.6 |  |  | 1,136 |  | 0.8 |
Acquisition costs | 122 |  | 1.0 |  |  | 1,997 |  | 20.8 |  |  | 241 |  | 0.2 |  |  | 2,317 |  | 1.7 |
Settlement of equity awards | — |  | — |  |  | — |  | — |  |  | (990 | ) | (0.9 | ) |  | (1,439 | ) | (1.0 | )
Other | 814 |  | 7.0 |  |  | (649 | ) | (6.8 | ) |  | (680 | ) | (0.6 | ) |  | (1,663 | ) | (1.2 | )
Total income tax expense | $ | 1,548 |  | 13.3 | % |  | $ | 5,153 |  | 53.6 | % |  | $ | 17,467 |  | 16.1 | % |  | $ | 51,548 |  | 36.9 | %

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- Definition The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -URI http://asc.fasb.org/topic&trid=2144680 + Details
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