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Common Equity (Tables) | 3 Months Ended
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Mar. 31, 2021
Schedule of Capitalization, Equity [Line Items] |
Common Share Activity | A summary of Alliant Energy’s common stock activity was as follows:
Shares outstanding, January 1, 2021 | 249,868,415 |
Shareowner Direct Plan | 152,588 |
Equity-based compensation plans | 113,549 |
Shares outstanding, March 31, 2021 | 250,134,552 |
Changes in Shareowners' Equity | A summary of changes in shareowners’ equity was as follows (in millions):
Alliant Energy | Total Alliant Energy Common Equity |  |  |  |
|  |  |  |  |  |  | Accumulated |  | Shares in |  | Cumulative |  |
|  |  | Additional |  |  |  | Other |  | Deferred |  | Preferred |  |
| Common |  | Paid-In |  | Retained |  | Comprehensive |  | Compensation |  | Stock |  | Total
| Stock |  | Capital |  | Earnings |  | Income (Loss) |  | Trust |  | of IPL |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $2 |  | $2,704 |  | $2,994 |  | ($1) |  | ($11) |  | $200 |  | $5,888
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 171 |  |  |  |  |  |  |  | 171
Common stock dividends ($0.4025 per share) |  |  |  |  | (102) |  |  |  |  |  |  |  | (102)
Shareowner Direct Plan issuances | 1 |  | 7 |  |  |  |  |  |  |  |  |  | 8
Equity-based compensation plans and other |  |  | 1 |  |  |  |  |  |  |  |  |  | 1
Ending balance, March 31, 2021 | $3 |  | $2,712 |  | $3,063 |  | ($1) |  | ($11) |  | $200 |  | $5,966
Three Months Ended March 31, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $2 |  | $2,446 |  | $2,766 |  | $1 |  | ($10) |  | $200 |  | $5,405
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 170 |  |  |  |  |  |  |  | 170
Common stock dividends ($0.38 per share) |  |  |  |  | (93) |  |  |  |  |  |  |  | (93)
Equity forward settlements and Shareowner Direct Plan issuances |  |  | 228 |  |  |  |  |  |  |  |  |  | 228
Adoption of new accounting standard, net of tax |  |  |  |  | (9) |  |  |  |  |  |  |  | (9)
Other comprehensive income, net of tax |  |  |  |  |  |  | 1 |  |  |  |  |  | 1
Ending balance, March 31, 2020 | $2 |  | $2,674 |  | $2,834 |  | $2 |  | ($10) |  | $200 |  | $5,702
IPL | Total IPL Common Equity |  |  |  |
|  |  | Additional |  |  |  | Cumulative |  |
| Common |  | Paid-In |  | Retained |  | Preferred |  | Total
| Stock |  | Capital |  | Earnings |  | Stock |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $33 |  | $2,752 |  | $979 |  | $200 |  | $3,964
Net income available for common stock |  |  |  |  | 79 |  |  |  | 79
Common stock dividends |  |  |  |  | (101) |  |  |  | (101)
Ending balance, March 31, 2021 | $33 |  | $2,752 |  | $957 |  | $200 |  | $3,942
Three Months Ended March 31, 2020 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $33 |  | $2,348 |  | $891 |  | $200 |  | $3,472
Net income available for common stock |  |  |  |  | 83 |  |  |  | 83
Common stock dividends |  |  |  |  | (60) |  |  |  | (60)
Capital contributions from parent |  |  | 100 |  |  |  |  |  | 100
Ending balance, March 31, 2020 | $33 |  | $2,448 |  | $914 |  | $200 |  | $3,595
WPL |  |  | Additional |  |  |  | Total
| Common |  | Paid-In |  | Retained |  | Common
| Stock |  | Capital |  | Earnings |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $66 |  | $1,459 |  | $953 |  | $2,478
Net income |  |  |  |  | 84 |  | 84
Common stock dividends |  |  |  |  | (42) |  | (42)
Capital contributions from parent |  |  | 125 |  |  |  | 125
Ending balance, March 31, 2021 | $66 |  | $1,584 |  | $995 |  | $2,645
Three Months Ended March 31, 2020 |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $66 |  | $1,434 |  | $864 |  | $2,364
Net income |  |  |  |  | 90 |  | 90
Common stock dividends |  |  |  |  | (43) |  | (43)
Capital contributions from parent |  |  | 25 |  |  |  | 25
Ending balance, March 31, 2020 | $66 |  | $1,459 |  | $911 |  | $2,436
IPL [Member] |
Schedule of Capitalization, Equity [Line Items] |
Changes in Shareowners' Equity | A summary of changes in shareowners’ equity was as follows (in millions):
Alliant Energy | Total Alliant Energy Common Equity |  |  |  |
|  |  |  |  |  |  | Accumulated |  | Shares in |  | Cumulative |  |
|  |  | Additional |  |  |  | Other |  | Deferred |  | Preferred |  |
| Common |  | Paid-In |  | Retained |  | Comprehensive |  | Compensation |  | Stock |  | Total
| Stock |  | Capital |  | Earnings |  | Income (Loss) |  | Trust |  | of IPL |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $2 |  | $2,704 |  | $2,994 |  | ($1) |  | ($11) |  | $200 |  | $5,888
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 171 |  |  |  |  |  |  |  | 171
Common stock dividends ($0.4025 per share) |  |  |  |  | (102) |  |  |  |  |  |  |  | (102)
Shareowner Direct Plan issuances | 1 |  | 7 |  |  |  |  |  |  |  |  |  | 8
Equity-based compensation plans and other |  |  | 1 |  |  |  |  |  |  |  |  |  | 1
Ending balance, March 31, 2021 | $3 |  | $2,712 |  | $3,063 |  | ($1) |  | ($11) |  | $200 |  | $5,966
Three Months Ended March 31, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $2 |  | $2,446 |  | $2,766 |  | $1 |  | ($10) |  | $200 |  | $5,405
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 170 |  |  |  |  |  |  |  | 170
Common stock dividends ($0.38 per share) |  |  |  |  | (93) |  |  |  |  |  |  |  | (93)
Equity forward settlements and Shareowner Direct Plan issuances |  |  | 228 |  |  |  |  |  |  |  |  |  | 228
Adoption of new accounting standard, net of tax |  |  |  |  | (9) |  |  |  |  |  |  |  | (9)
Other comprehensive income, net of tax |  |  |  |  |  |  | 1 |  |  |  |  |  | 1
Ending balance, March 31, 2020 | $2 |  | $2,674 |  | $2,834 |  | $2 |  | ($10) |  | $200 |  | $5,702
IPL | Total IPL Common Equity |  |  |  |
|  |  | Additional |  |  |  | Cumulative |  |
| Common |  | Paid-In |  | Retained |  | Preferred |  | Total
| Stock |  | Capital |  | Earnings |  | Stock |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $33 |  | $2,752 |  | $979 |  | $200 |  | $3,964
Net income available for common stock |  |  |  |  | 79 |  |  |  | 79
Common stock dividends |  |  |  |  | (101) |  |  |  | (101)
Ending balance, March 31, 2021 | $33 |  | $2,752 |  | $957 |  | $200 |  | $3,942
Three Months Ended March 31, 2020 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $33 |  | $2,348 |  | $891 |  | $200 |  | $3,472
Net income available for common stock |  |  |  |  | 83 |  |  |  | 83
Common stock dividends |  |  |  |  | (60) |  |  |  | (60)
Capital contributions from parent |  |  | 100 |  |  |  |  |  | 100
Ending balance, March 31, 2020 | $33 |  | $2,448 |  | $914 |  | $200 |  | $3,595
WPL |  |  | Additional |  |  |  | Total
| Common |  | Paid-In |  | Retained |  | Common
| Stock |  | Capital |  | Earnings |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $66 |  | $1,459 |  | $953 |  | $2,478
Net income |  |  |  |  | 84 |  | 84
Common stock dividends |  |  |  |  | (42) |  | (42)
Capital contributions from parent |  |  | 125 |  |  |  | 125
Ending balance, March 31, 2021 | $66 |  | $1,584 |  | $995 |  | $2,645
Three Months Ended March 31, 2020 |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $66 |  | $1,434 |  | $864 |  | $2,364
Net income |  |  |  |  | 90 |  | 90
Common stock dividends |  |  |  |  | (43) |  | (43)
Capital contributions from parent |  |  | 25 |  |  |  | 25
Ending balance, March 31, 2020 | $66 |  | $1,459 |  | $911 |  | $2,436
WPL [Member] |
Schedule of Capitalization, Equity [Line Items] |
Changes in Shareowners' Equity | A summary of changes in shareowners’ equity was as follows (in millions):
Alliant Energy | Total Alliant Energy Common Equity |  |  |  |
|  |  |  |  |  |  | Accumulated |  | Shares in |  | Cumulative |  |
|  |  | Additional |  |  |  | Other |  | Deferred |  | Preferred |  |
| Common |  | Paid-In |  | Retained |  | Comprehensive |  | Compensation |  | Stock |  | Total
| Stock |  | Capital |  | Earnings |  | Income (Loss) |  | Trust |  | of IPL |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $2 |  | $2,704 |  | $2,994 |  | ($1) |  | ($11) |  | $200 |  | $5,888
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 171 |  |  |  |  |  |  |  | 171
Common stock dividends ($0.4025 per share) |  |  |  |  | (102) |  |  |  |  |  |  |  | (102)
Shareowner Direct Plan issuances | 1 |  | 7 |  |  |  |  |  |  |  |  |  | 8
Equity-based compensation plans and other |  |  | 1 |  |  |  |  |  |  |  |  |  | 1
Ending balance, March 31, 2021 | $3 |  | $2,712 |  | $3,063 |  | ($1) |  | ($11) |  | $200 |  | $5,966
Three Months Ended March 31, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $2 |  | $2,446 |  | $2,766 |  | $1 |  | ($10) |  | $200 |  | $5,405
Net income attributable to Alliant Energy common shareowners |  |  |  |  | 170 |  |  |  |  |  |  |  | 170
Common stock dividends ($0.38 per share) |  |  |  |  | (93) |  |  |  |  |  |  |  | (93)
Equity forward settlements and Shareowner Direct Plan issuances |  |  | 228 |  |  |  |  |  |  |  |  |  | 228
Adoption of new accounting standard, net of tax |  |  |  |  | (9) |  |  |  |  |  |  |  | (9)
Other comprehensive income, net of tax |  |  |  |  |  |  | 1 |  |  |  |  |  | 1
Ending balance, March 31, 2020 | $2 |  | $2,674 |  | $2,834 |  | $2 |  | ($10) |  | $200 |  | $5,702
IPL | Total IPL Common Equity |  |  |  |
|  |  | Additional |  |  |  | Cumulative |  |
| Common |  | Paid-In |  | Retained |  | Preferred |  | Total
| Stock |  | Capital |  | Earnings |  | Stock |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $33 |  | $2,752 |  | $979 |  | $200 |  | $3,964
Net income available for common stock |  |  |  |  | 79 |  |  |  | 79
Common stock dividends |  |  |  |  | (101) |  |  |  | (101)
Ending balance, March 31, 2021 | $33 |  | $2,752 |  | $957 |  | $200 |  | $3,942
Three Months Ended March 31, 2020 |  |  |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $33 |  | $2,348 |  | $891 |  | $200 |  | $3,472
Net income available for common stock |  |  |  |  | 83 |  |  |  | 83
Common stock dividends |  |  |  |  | (60) |  |  |  | (60)
Capital contributions from parent |  |  | 100 |  |  |  |  |  | 100
Ending balance, March 31, 2020 | $33 |  | $2,448 |  | $914 |  | $200 |  | $3,595
WPL |  |  | Additional |  |  |  | Total
| Common |  | Paid-In |  | Retained |  | Common
| Stock |  | Capital |  | Earnings |  | Equity
Three Months Ended March 31, 2021 |  |  |  |  |  |  |
Beginning balance, December 31, 2020 | $66 |  | $1,459 |  | $953 |  | $2,478
Net income |  |  |  |  | 84 |  | 84
Common stock dividends |  |  |  |  | (42) |  | (42)
Capital contributions from parent |  |  | 125 |  |  |  | 125
Ending balance, March 31, 2021 | $66 |  | $1,584 |  | $995 |  | $2,645
Three Months Ended March 31, 2020 |  |  |  |  |  |  |
Beginning balance, December 31, 2019 | $66 |  | $1,434 |  | $864 |  | $2,364
Net income |  |  |  |  | 90 |  | 90
Common stock dividends |  |  |  |  | (43) |  | (43)
Capital contributions from parent |  |  | 25 |  |  |  | 25
Ending balance, March 31, 2020 | $66 |  | $1,459 |  | $911 |  | $2,436

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