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Income tax expense (benefit) statutory rate versus actual rate (Details 6) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Computed tax at federal statutory rate |  |  |
Computed tax at federal statutory rate | $ 97,032 | $ 97,997 | $ 99,775
Federal statutory rate | 21.00% | 21.00% | 21.00%
Increases (reductions) resulting from: |  |  |
State income taxes, net of federal income tax | $ 19,126 | $ 19,496 | $ 17,845
State income tax, rate | 4.10% | 4.20% | 3.80%
Federal renewable energy credit | $ (15,343) | $ (13,914) | $ (16,009)
Federal renewable energy credit, rate | (3.30%) | (3.00%) | (3.40%)
Tax compliance and uncertain tax positions | $ 1,080 | $ (477) | $ (3,543)
Tax compliance and uncertain tax positions, rate | 0.20% | (0.10%) | (0.70%)
Nonqualified benefit plans | $ 2,827 | $ (1,881) | $ (2,443)
Effective Income Tax Rate Nonqualified benefit plans | 0.60% | (0.40%) | (0.50%)
Excess deferred income tax amortization | $ (9,008) | $ (10,295) | $ (12,517)
Excess deferred income tax amortization, rate | (1.90%) | (2.20%) | (2.60%)
Other | $ (931) | $ (2,006) | $ 1,482
Other, rate | (0.20%) | (0.40%) | 0.20%
Income taxes | $ 94,783 | $ 88,920 | $ 84,590
Total income tax expense, rate | 20.50% | 19.10% | 17.80%

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