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Income Taxes (Tables) | 12 Months Ended
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Dec. 31, 2020
Income Tax Disclosure [Abstract] |
Components of income before income taxes | The components of income before income taxes from continuing operations for each of the years ended December 31 were as follows:
| 2020 | 2019 | 2018
| (In thousands)
United States | $ | 474,856 |  | $ | 398,532 |  | $ | 317,655 |
Foreign | 261 |  | (87) |  | (784) |
Income before income taxes from continuing operations | $ | 475,117 |  | $ | 398,445 |  | $ | 316,871 |
Income tax expense | Income tax expense (benefit) from continuing operations for the years ended December 31 was as follows:
| 2020 |  | 2019 |  | 2018 |
| (In thousands)
Current: |  |  |
Federal | $ | 65,006 |  | $ | (3,502) |  | $ | (15,901) |
State | 21,234 |  | 3,366 |  | 3,651 |
Foreign | 151 |  | — |  | — |
| 86,391 |  | (136) |  | (12,250) |
Deferred: |  |  |
Income taxes: |  |  |
Federal | (3,735) |  | 50,218 |  | 50,755 |
State | (625) |  | 12,098 |  | 7,206 |
Investment tax credit - net | 2,559 |  | 1,099 |  | 1,774 |
| (1,801) |  | 63,415 |  | 59,735 |
Total income tax expense | $ | 84,590 |  | $ | 63,279 |  | $ | 47,485 |
Deferred tax assets and deferred tax liabilities | Components of deferred tax assets and deferred tax liabilities at December 31 were as follows:
| 2020 | 2019
| (In thousands)
Deferred tax assets: |  |
Postretirement | $ | 51,495 |  | $ | 51,075 |
Compensation-related | 40,477 |  | 37,330 |
Operating lease liabilities | 25,963 |  | 24,459 |
Payroll tax deferral | 14,010 |  | — |
Legal and environmental contingencies | 9,467 |  | 6,601 |
Asset retirement obligations | 8,060 |  | 7,450 |
Customer advances | 7,463 |  | 7,325 |
Federal renewable energy credit | — |  | 5,343 |
Other | 37,944 |  | 32,533 |
Total deferred tax assets | 194,879 |  | 172,116 |
Deferred tax liabilities: |  |
Depreciation and basis differences on property, plant and equipment | 536,966 |  | 511,867 |
Postretirement | 49,233 |  | 48,927 |
Operating lease right-of-use-assets | 25,858 |  | 24,436 |
Intangible asset amortization | 19,514 |  | 18,930 |
Other | 67,922 |  | 61,385 |
Total deferred tax liabilities | 699,493 |  | 665,545 |
Valuation allowance | 11,484 |  | 13,154 |
Net deferred income tax liability | $ | 516,098 |  | $ | 506,583 |
Schedule of change in net deferred income tax liability reconciliation | The following table reconciles the change in the net deferred income tax liability from December 31, 2019, to December 31, 2020, to deferred income tax benefit:
| 2020
(In thousands)
Change in net deferred income tax liability from the preceding table | $ | 9,515 |
Deferred taxes associated with other comprehensive loss | 1,817 |
Excess deferred income tax amortization | (12,517) |
Other | (616) |
Deferred income tax benefit for the period | $ | (1,801) |
Reconciliation of income tax expense (benefit) at statutory federal rate versus actual rate | Total income tax expense differs from the amount computed by applying the statutory federal income tax rate to income before taxes. The reasons for this difference were as follows:
Years ended December 31, | 2020 | 2019 | 2018
| Amount | % | Amount | % | Amount | %
| (Dollars in thousands)
Computed tax at federal statutory rate | $ | 99,775 |  | 21.0 |  | $ | 83,674 |  | 21.0 |  | $ | 66,543 |  | 21.0 |
Increases (reductions) resulting from: |  |  |  |  |  |
State income taxes, net of federal income tax | 17,845 |  | 3.8 |  | 14,029 |  | 3.5 |  | 12,190 |  | 3.8 |
Federal renewable energy credit | (16,009) |  | (3.4) |  | (15,843) |  | (4.0) |  | (11,759) |  | (3.7) |
Tax compliance and uncertain tax positions | (3,543) |  | (.7) |  | (2,739) |  | (.7) |  | (2,725) |  | (.9) |
Excess deferred income tax amortization | (12,517) |  | (2.6) |  | (11,904) |  | (3.0) |  | (9,319) |  | (2.9) |
TCJA revaluation | — |  | — |  | — |  | — |  | (5,947) |  | (1.9) |
TCJA revaluation related to accumulated other comprehensive loss balance | — |  | — |  | — |  | — |  | (42) |  | — |
Other | (961) |  | (.3) |  | (3,938) |  | (.9) |  | (1,456) |  | (.4) |
Total income tax expense | $ | 84,590 |  | 17.8 |  | $ | 63,279 |  | 15.9 |  | $ | 47,485 |  | 15.0 |

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