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Income Taxes (Tables) | 12 Months Ended
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Dec. 31, 2023
Income Tax Disclosure [Abstract] |
Schedule of Components of Income Tax Expense (Benefit) | The following table sets forth our provision for income taxes for the periods indicated:
| Years Ended December 31,
| 2023 |  | 2022 |  | 2021
| (Thousands of dollars)
Current income tax provision (benefit) |  |  |  |  |
Federal | $ | 16,551 |  |  | $ | 61,745 |  |  | $ | (1,568) |
State | (829) |  |  | 6,815 |  |  | (1,565) |
Total current income tax provision (benefit) | 15,722 |  |  | 68,560 |  |  | (3,133) |
Deferred income tax provision (benefit) |  |  |  |  |
Federal | 21,905 |  |  | (22,234) |  |  | 37,810 |
State | 2,868 |  |  | 200 |  |  | 5,639 |
Total deferred income tax provision (benefit) | 24,773 |  |  | (22,034) |  |  | 43,449 |
Total provision for income taxes | $ | 40,495 |  |  | $ | 46,526 |  |  | $ | 40,316 |
Schedule of Effective Income Tax Rate Reconciliation | The following table is a reconciliation of our income tax provision for the periods indicated:
| Years Ended December 31,
| 2023 |  | 2022 |  | 2021
| (Thousands of dollars)
Income before income taxes | $ | 271,727 |  |  | $ | 268,268 |  |  | $ | 246,750 |
Federal statutory income tax rate | 21 | % |  | 21 | % |  | 21 | %
Provision for federal income taxes | 57,063 |  |  | 56,335 |  |  | 51,817 |
State income taxes, net of federal tax benefit | 3,834 |  |  | 7,016 |  |  | 4,074 |
Amortization of excess deferred federal income taxes | (20,565) |  |  | (17,986) |  |  | (17,289) |
Amortization of excess deferred state income taxes | (1,795) |  |  | — |  |  | — |
Tax (expense) benefit for employee share-based compensation | 418 |  |  | 350 |  |  | (469) |
Other, net | 1,540 |  |  | 811 |  |  | 2,183 |
Total provision for income taxes | $ | 40,495 |  |  | $ | 46,526 |  |  | $ | 40,316 |
Schedule of Deferred Tax Assets and Liabilities | The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated:
| December 31,
| 2023 |  | 2022
| (Thousands of dollars)
Deferred tax assets |  |  |
Employee benefits and other accrued liabilities | $ | — |  |  | $ | 4,256 |
Regulatory adjustments for enacted tax rate changes | 107,948 |  |  | 114,551 |
Net operating loss | 93,255 |  |  | 161,320 |
Lease obligation basis | 4,500 |  |  | 9,158 |
Purchased-gas cost adjustment | 5,232 |  |  | 3,384 |
Other | — |  |  | 3,014 |
Total deferred tax assets | 210,935 |  |  | 295,683 |
Deferred tax liabilities |  |  |
Excess of tax over book depreciation | 822,619 |  |  | 792,570 |
Winter weather event costs | 56,914 |  |  | 121,347 |
Other regulatory assets and liabilities, net | 70,384 |  |  | 71,180 |
Employee benefits and other accrued liabilities | 205 |  |  | — |
Right-of-use asset basis | 4,662 |  |  | 9,042 |
Other | 8,219 |  |  | — |
Total deferred tax liabilities | 963,003 |  |  | 994,139 |
Net deferred tax liabilities | $ | 752,068 |  |  | $ | 698,456 |

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- Definition Tabular disclosure of the components of income tax expense attributable to continuing operations for each year presented including, but not limited to: current tax expense (benefit), deferred tax expense (benefit), investment tax credits, government grants, the benefits of operating loss carryforwards, tax expense that results from allocating certain tax benefits either directly to contributed capital or to reduce goodwill or other noncurrent intangible assets of an acquired entity, adjustments of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity, and adjustments of the beginning-of-the-year balances of a valuation allowance because of a change in circumstances that causes a change in judgment about the realizability of the related deferred tax asset in future years. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Paragraph 9 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-9 + Details
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- Definition Tabular disclosure of the components of net deferred tax asset or liability recognized in an entity's statement of financial position, including the following: the total of all deferred tax liabilities, the total of all deferred tax assets, the total valuation allowance recognized for deferred tax assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Paragraph 2 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-2 + Details
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