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Income Taxes (Schedule Of Effective Income Rate Reconciliation) (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Income Taxes [Line Items] |  |  |  |
Income from continuing operations before income taxes |  | $ 774 | $ 886 | $ 826
Income tax expense at statutory rate |  | 163 | 310 | 289
Increase (decrease) in income taxes from: |  |  |  |
State and local income taxes, net of federal effect |  | 46 | 26 | 37
Accelerated flow-through of regulatory tax benefits2 |  | (39) | (39) | (39)
TCJA excess deferred taxes |  | (26) | 0 | 0
Production tax credits |  | (14) | (8) | (9)
Research and development tax credits, net |  | (11) | (1) | (2)
Impact of the TCJA |  | (4) | 148 | 0
Other, net |  | 0 | (12) | (3)
Tax expense |  | $ 115 | $ 424 | $ 273
Effective tax rate |  | 14.90% | 47.90% | 33.10%
Income tax benefit |  |  | $ 14 |
Valuation allowance |  | $ 8 | 15 |
Consumers Energy Company |  |  |  |
Income Taxes [Line Items] |  |  |  |
Income from continuing operations before income taxes |  | 847 | 971 | $ 936
Income tax expense at statutory rate |  | 178 | 340 | 328
Increase (decrease) in income taxes from: |  |  |  |
State and local income taxes, net of federal effect |  | 51 | 30 | 44
Accelerated flow-through of regulatory tax benefits2 |  | (39) | (39) | (39)
TCJA excess deferred taxes |  | (26) | 0 | 0
Production tax credits |  | (12) | (8) | (9)
Research and development tax credits, net |  | (11) | (1) | (2)
Impact of the TCJA |  | 1 | 33 | 0
Other, net |  | 0 | (16) | (2)
Tax expense |  | $ 142 | $ 339 | $ 320
Effective tax rate |  | 16.80% | 34.90% | 34.20%
Reduction of income tax expense |  | $ 39 | $ 39 | $ 39
Net regulatory tax liability |  | 3,836 | 3,795 |
Plant, property, and equipment (subject to normalization) | Consumers Energy Company |  |  |  |
Increase (decrease) in income taxes from: |  |  |  |
Net regulatory tax liability |  |  | $ 1,800 |
Revenue Subject To Refund Tax Reform Dfit Change | Consumers Energy Company |  |  |  |
Increase (decrease) in income taxes from: |  |  |  |
Net regulatory tax liability |  | 35 |  |
Research Tax Credit Carryforward | Consumers Energy Company |  |  |  |
Increase (decrease) in income taxes from: |  |  |  |
Increase in tax credit carryforward | $ 8 |  |  |
Eliminate Write Off of Alternative Minimum Tax Credits |  |  |  |
Increase (decrease) in income taxes from: |  |  |  |
Valuation allowance |  | $ 9 |  |

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