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Income Taxes | 3 Months Ended
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Mar. 31, 2022
Income Taxes [Line Items] |
Income Taxes | INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL.
| Alliant Energy |  | IPL |  | WPL
| 2022 |  | 2021 |  |  |  |  |  | 2022 |  | 2021 |  |  |  |  |  | 2022 |  | 2021 |  |  |  |
Overall income tax rate | 4% |  | (19%) |  |  |  |  |  | (14%) |  | (17%) |  |  |  |  |  | 19% |  | (29%) |  |  |  |
Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2037 |  | $94 |  | $87 |  | $1
State net operating losses | 2022-2042 |  | 578 |  | 13 |  | 2
Federal tax credits | 2022-2042 |  | 589 |  | 369 |  | 197
Iowa Tax Reform - In March 2022, Iowa tax reform was enacted, which would reduce the current 9.8% Iowa corporate income tax rate beginning in 2023 if certain state income tax revenue triggers are satisfied. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year. Rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%. Alliant Energy is currently unable to predict with certainty the timing or amount of any rate reductions. The majority of any reduction in income tax expense as a result of the lower Iowa corporate income tax rate is currently expected to reduce rates for IPL’s customers. In addition, after the 2023 corporate income tax rate is known in the fourth quarter of 2022, Alliant Energy currently expects to record a charge related to the remeasurement of accumulated deferred income tax assets at its non-utility businesses.
IPL [Member] |
Income Taxes [Line Items] |
Income Taxes | INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL.
| Alliant Energy |  | IPL |  | WPL
| 2022 |  | 2021 |  |  |  |  |  | 2022 |  | 2021 |  |  |  |  |  | 2022 |  | 2021 |  |  |  |
Overall income tax rate | 4% |  | (19%) |  |  |  |  |  | (14%) |  | (17%) |  |  |  |  |  | 19% |  | (29%) |  |  |  |
Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2037 |  | $94 |  | $87 |  | $1
State net operating losses | 2022-2042 |  | 578 |  | 13 |  | 2
Federal tax credits | 2022-2042 |  | 589 |  | 369 |  | 197
Iowa Tax Reform - In March 2022, Iowa tax reform was enacted, which would reduce the current 9.8% Iowa corporate income tax rate beginning in 2023 if certain state income tax revenue triggers are satisfied. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year. Rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%. Alliant Energy is currently unable to predict with certainty the timing or amount of any rate reductions. The majority of any reduction in income tax expense as a result of the lower Iowa corporate income tax rate is currently expected to reduce rates for IPL’s customers. In addition, after the 2023 corporate income tax rate is known in the fourth quarter of 2022, Alliant Energy currently expects to record a charge related to the remeasurement of accumulated deferred income tax assets at its non-utility businesses.
WPL [Member] |
Income Taxes [Line Items] |
Income Taxes | INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL.
| Alliant Energy |  | IPL |  | WPL
| 2022 |  | 2021 |  |  |  |  |  | 2022 |  | 2021 |  |  |  |  |  | 2022 |  | 2021 |  |  |  |
Overall income tax rate | 4% |  | (19%) |  |  |  |  |  | (14%) |  | (17%) |  |  |  |  |  | 19% |  | (29%) |  |  |  |
Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):
| Range of Expiration Dates |  | Alliant Energy |  | IPL |  | WPL
Federal net operating losses | 2037 |  | $94 |  | $87 |  | $1
State net operating losses | 2022-2042 |  | 578 |  | 13 |  | 2
Federal tax credits | 2022-2042 |  | 589 |  | 369 |  | 197
Iowa Tax Reform - In March 2022, Iowa tax reform was enacted, which would reduce the current 9.8% Iowa corporate income tax rate beginning in 2023 if certain state income tax revenue triggers are satisfied. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year. Rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%. Alliant Energy is currently unable to predict with certainty the timing or amount of any rate reductions. The majority of any reduction in income tax expense as a result of the lower Iowa corporate income tax rate is currently expected to reduce rates for IPL’s customers. In addition, after the 2023 corporate income tax rate is known in the fourth quarter of 2022, Alliant Energy currently expects to record a charge related to the remeasurement of accumulated deferred income tax assets at its non-utility businesses.

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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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 21 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 11.C) -URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 17 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.5.Q1) -URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 270 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -URI http://asc.fasb.org/topic&trid=2144680 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)(2)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 + Details
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