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Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance |  |  | $ 6,777 |
Beginning balance | $ 6,791 | $ 6,452 | 6,777 | $ 6,276
Net income attributable to common shareowners | 295 | 259 | 540 | 582
Net income |  |  | 540 | 582
Common stock dividends | (123) | (115) | (369) | (341)
At-the-market offering program and Shareowner Direct Plan issuances | 6 | 125 | 18 | 201
Equity-based compensation plans and other | 3 | 4 | 4 | 4
Other comprehensive income (loss), net of tax | (4) | 1 | (2) | 4
Ending balance | 6,968 |  | 6,968 |
Ending balance | $ 6,968 | $ 6,726 | $ 6,968 | $ 6,726
Common stock dividends (in dollars per share) | $ 0.48 | $ 0.4525 | $ 1.44 | $ 1.3575
Common Stock [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | $ 3 | $ 3 | $ 3 | $ 3
Ending balance | 3 | 3 | 3 | 3
Additional Paid-in Capital [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 3,042 | 2,854 | 3,030 | 2,777
At-the-market offering program and Shareowner Direct Plan issuances | 6 | 125 | 18 | 201
Equity-based compensation plans and other | 4 | 3 | 4 | 4
Ending balance | 3,052 | 2,982 | 3,052 | 2,982
Retained Earnings [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 3,755 | 3,606 | 3,756 | 3,509
Net income attributable to common shareowners | 295 | 259 | 540 | 582
Common stock dividends | (123) | (115) | (369) | (341)
Ending balance | 3,927 | 3,750 | 3,927 | 3,750
Accumulated Other Comprehensive Income (Loss) [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 3 | 3 | 1 | 0
Other comprehensive income (loss), net of tax | (4) | 1 | (2) | 4
Ending balance | (1) | 4 | (1) | 4
Shares in Deferred Compensation Trust [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | (12) | (14) | (13) | (13)
Equity-based compensation plans and other | (1) | 1 |  |
Ending balance | (13) | (13) | (13) | (13)
IPL [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance |  |  | 3,974 |
Beginning balance | 4,080 | 3,869 | 3,974 | 3,808
Net income attributable to common shareowners | 190 | 170 | 272 | 331
Net income | 190 | 170 | 272 | 331
Common stock dividends | (50) | (70) | (151) | (210)
Capital contributions from parent | 200 | 20 | 325 | 60
Ending balance | 4,420 |  | 4,420 |
Ending balance | 4,420 | 3,989 | 4,420 | 3,989
IPL [Member] | Common Stock [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 33 | 33 | 33 | 33
Ending balance | 33 | 33 | 33 | 33
IPL [Member] | Additional Paid-in Capital [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 3,012 | 2,847 | 2,887 | 2,807
Capital contributions from parent | 200 | 20 | 325 | 60
Ending balance | 3,212 | 2,867 | 3,212 | 2,867
IPL [Member] | Retained Earnings [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 1,035 | 989 | 1,054 | 968
Net income | 190 | 170 | 272 | 331
Common stock dividends | (50) | (70) | (151) | (210)
Ending balance | 1,175 | 1,089 | 1,175 | 1,089
WPL [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance |  |  | 3,897 |
Beginning balance | 4,010 | 3,739 | 3,897 | 3,491
Net income attributable to common shareowners | 114 | 107 | 270 | 267
Net income | 114 | 107 | 270 | 267
Common stock dividends | (49) | (46) | (147) | (138)
Capital contributions from parent |  | 65 | 55 | 245
Ending balance | 4,075 |  | 4,075 |
Ending balance | 4,075 | 3,865 | 4,075 | 3,865
WPL [Member] | Common Stock [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 66 | 66 | 66 | 66
Ending balance | 66 | 66 | 66 | 66
WPL [Member] | Additional Paid-in Capital [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 2,533 | 2,413 | 2,478 | 2,233
Capital contributions from parent |  | 65 | 55 | 245
Ending balance | 2,533 | 2,478 | 2,533 | 2,478
WPL [Member] | Retained Earnings [Member] |  |  |  |
Changes in Shareowners' Equity Roll Forward [Line Items] |  |  |  |
Beginning balance | 1,411 | 1,260 | 1,353 | 1,192
Net income | 114 | 107 | 270 | 267
Common stock dividends | (49) | (46) | (147) | (138)
Ending balance | $ 1,476 | $ 1,321 | $ 1,476 | $ 1,321

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