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Common Equity | 12 Months Ended
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Dec. 31, 2016
Schedule of Common Equity [Line Items] |
Common Equity | COMMON EQUITY Common Stock Split - On April 20, 2016, Alliant Energy’s Board of Directors approved a two-for-one common stock split and a proportionate increase in the number of authorized shares of common stock of Alliant Energy from 240 million shares to 480 million shares to implement the stock split. Alliant Energy shareowners of record at the close of business on May 4, 2016 received one additional share of Alliant Energy common stock for each share held on that date. The proportionate interest that a shareowner owns in Alliant Energy did not change as a result of the stock split. The additional shares were distributed on May 19, 2016 and post-split trading began on May 20, 2016. All Alliant Energy share and per share amounts in this report have been reflected on a post-split basis. Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:
| 2016 |  | 2015 |  | 2014
Shares outstanding, January 1 | 226,918,432 |  |  | 221,871,360 |  |  | 221,887,338 |
At-the-market offering program | — |  |  | 4,373,234 |  |  | — |
Shareowner Direct Plan issuances | 732,814 |  |  | 606,010 |  |  | — |
Equity-based compensation plans (Note 12(b)) | 22,408 |  |  | 112,756 |  |  | 71,094 |
Other | — |  |  | (44,928 | ) |  | (87,072 | )
Shares outstanding, December 31 | 227,673,654 |  |  | 226,918,432 |  |  | 221,871,360 |
At December 31, 2016, Alliant Energy had a total of 11.3 million shares available for issuance in the aggregate, pursuant to its Amended and Restated OIP, Shareowner Direct Plan and 401(k) Savings Plan. At-the-Market Offering Program - In 2015, Alliant Energy filed a prospectus supplement under which it may sell up to $150 million of its common stock through an at-the-market offering program. In 2015, Alliant Energy issued 4,373,234 shares of common stock through this program and received cash proceeds of $133 million, net of $2 million in fees and commissions. The proceeds from the issuances of common stock were used for general corporate purposes. This at-the-market offering program expired in 2016. Shareowner Direct Plan - Beginning in 2015, Alliant Energy satisfied its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market. Shareowner Rights Agreement - Alliant Energy has established an amended and restated Shareowner Rights Agreement. The rights under this agreement will only become exercisable if a person or group has acquired, or announced an intention to acquire, 15% or more of Alliant Energy’s outstanding common stock. Each right will initially entitle registered shareowners to purchase from Alliant Energy one-quarter of one share of Alliant Energy’s common stock. The rights will be exercisable at an initial price of $55.00 per full share, subject to adjustment. If any shareowner acquires 15% or more of the outstanding common stock of Alliant Energy, each right (subject to limitations) will entitle its holder to purchase, at the right’s then current exercise price, a number of common shares of Alliant Energy or of the acquirer having a market value at the time of twice the right’s per full share exercise price. Alliant Energy’s Board of Directors is authorized to reduce the 15% ownership threshold to not less than 10%. The amended and restated Shareowner Rights Agreement expires in December 2018. Alliant Energy currently has no intention to redeem the Shareowner Rights Agreement and plans to allow it to naturally expire at the end of the term. Dividend Restrictions - Alliant Energy does not have any significant common stock dividend restrictions. IPL and WPL each have common stock dividend restrictions based on applicable regulatory limitations. IPL also has common stock dividend restrictions based on the terms of its outstanding preferred stock. As of December 31, 2016, IPL and WPL were in compliance with all such dividend restrictions. IPL is restricted from paying common stock dividends to its parent company, Alliant Energy, if for any past or current dividend period, dividends on its preferred stock have not been paid, or declared and set apart for payment. IPL has paid all dividends on its preferred stock through 2016. Under the Federal Power Act, IPL may not pay dividends to its parent company in excess of the current amount of its retained earnings. As of December 31, 2016, IPL’s amount of retained earnings that were free of dividend restrictions was $618 million. If IPL’s actual 13-month average common equity ratio (calculated on a financial basis consistent with IPL’s rate cases) falls below 42% of total capitalization, IPL is required to notify the IUB. Pursuant to a December 2016 PSCW order, WPL has a regulatory limitation on distributions to its parent company. WPL is prohibited from paying annual common stock dividends to its parent company in excess of forecasted dividend levels of $126 million in 2017 and $140 million in 2018 if WPL’s actual 13-month average common equity ratio (calculated on a financial basis consistent with WPL’s rate cases) would fall below 51.00% for 2017 or 2018. As of December 31, 2016, WPL’s amount of retained earnings that were free of dividend restrictions was $126 million for 2017. Restricted Net Assets of Subsidiaries - IPL and WPL do not have regulatory authority to lend or advance any amounts to their parent company. As of December 31, 2016, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company, Alliant Energy, in the form of loans, advances or cash dividends without the consent of IPL’s and WPL’s regulatory authorities was $1.6 billion for each. Comprehensive Income - In 2016, 2015 and 2014, Alliant Energy’s other comprehensive income (loss) was $0, $0.2 million and ($0.4) million, respectively; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. In 2016, 2015 and 2014, IPL and WPL had no other comprehensive income; therefore their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.
IPL [Member] |
Schedule of Common Equity [Line Items] |
Common Equity | COMMON EQUITY Common Stock Split - On April 20, 2016, Alliant Energy’s Board of Directors approved a two-for-one common stock split and a proportionate increase in the number of authorized shares of common stock of Alliant Energy from 240 million shares to 480 million shares to implement the stock split. Alliant Energy shareowners of record at the close of business on May 4, 2016 received one additional share of Alliant Energy common stock for each share held on that date. The proportionate interest that a shareowner owns in Alliant Energy did not change as a result of the stock split. The additional shares were distributed on May 19, 2016 and post-split trading began on May 20, 2016. All Alliant Energy share and per share amounts in this report have been reflected on a post-split basis. Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:
| 2016 |  | 2015 |  | 2014
Shares outstanding, January 1 | 226,918,432 |  |  | 221,871,360 |  |  | 221,887,338 |
At-the-market offering program | — |  |  | 4,373,234 |  |  | — |
Shareowner Direct Plan issuances | 732,814 |  |  | 606,010 |  |  | — |
Equity-based compensation plans (Note 12(b)) | 22,408 |  |  | 112,756 |  |  | 71,094 |
Other | — |  |  | (44,928 | ) |  | (87,072 | )
Shares outstanding, December 31 | 227,673,654 |  |  | 226,918,432 |  |  | 221,871,360 |
At December 31, 2016, Alliant Energy had a total of 11.3 million shares available for issuance in the aggregate, pursuant to its Amended and Restated OIP, Shareowner Direct Plan and 401(k) Savings Plan. At-the-Market Offering Program - In 2015, Alliant Energy filed a prospectus supplement under which it may sell up to $150 million of its common stock through an at-the-market offering program. In 2015, Alliant Energy issued 4,373,234 shares of common stock through this program and received cash proceeds of $133 million, net of $2 million in fees and commissions. The proceeds from the issuances of common stock were used for general corporate purposes. This at-the-market offering program expired in 2016. Shareowner Direct Plan - Beginning in 2015, Alliant Energy satisfied its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market. Shareowner Rights Agreement - Alliant Energy has established an amended and restated Shareowner Rights Agreement. The rights under this agreement will only become exercisable if a person or group has acquired, or announced an intention to acquire, 15% or more of Alliant Energy’s outstanding common stock. Each right will initially entitle registered shareowners to purchase from Alliant Energy one-quarter of one share of Alliant Energy’s common stock. The rights will be exercisable at an initial price of $55.00 per full share, subject to adjustment. If any shareowner acquires 15% or more of the outstanding common stock of Alliant Energy, each right (subject to limitations) will entitle its holder to purchase, at the right’s then current exercise price, a number of common shares of Alliant Energy or of the acquirer having a market value at the time of twice the right’s per full share exercise price. Alliant Energy’s Board of Directors is authorized to reduce the 15% ownership threshold to not less than 10%. The amended and restated Shareowner Rights Agreement expires in December 2018. Alliant Energy currently has no intention to redeem the Shareowner Rights Agreement and plans to allow it to naturally expire at the end of the term. Dividend Restrictions - Alliant Energy does not have any significant common stock dividend restrictions. IPL and WPL each have common stock dividend restrictions based on applicable regulatory limitations. IPL also has common stock dividend restrictions based on the terms of its outstanding preferred stock. As of December 31, 2016, IPL and WPL were in compliance with all such dividend restrictions. IPL is restricted from paying common stock dividends to its parent company, Alliant Energy, if for any past or current dividend period, dividends on its preferred stock have not been paid, or declared and set apart for payment. IPL has paid all dividends on its preferred stock through 2016. Under the Federal Power Act, IPL may not pay dividends to its parent company in excess of the current amount of its retained earnings. As of December 31, 2016, IPL’s amount of retained earnings that were free of dividend restrictions was $618 million. If IPL’s actual 13-month average common equity ratio (calculated on a financial basis consistent with IPL’s rate cases) falls below 42% of total capitalization, IPL is required to notify the IUB. Pursuant to a December 2016 PSCW order, WPL has a regulatory limitation on distributions to its parent company. WPL is prohibited from paying annual common stock dividends to its parent company in excess of forecasted dividend levels of $126 million in 2017 and $140 million in 2018 if WPL’s actual 13-month average common equity ratio (calculated on a financial basis consistent with WPL’s rate cases) would fall below 51.00% for 2017 or 2018. As of December 31, 2016, WPL’s amount of retained earnings that were free of dividend restrictions was $126 million for 2017. Restricted Net Assets of Subsidiaries - IPL and WPL do not have regulatory authority to lend or advance any amounts to their parent company. As of December 31, 2016, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company, Alliant Energy, in the form of loans, advances or cash dividends without the consent of IPL’s and WPL’s regulatory authorities was $1.6 billion for each. Comprehensive Income - In 2016, 2015 and 2014, Alliant Energy’s other comprehensive income (loss) was $0, $0.2 million and ($0.4) million, respectively; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. In 2016, 2015 and 2014, IPL and WPL had no other comprehensive income; therefore their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.
WPL [Member] |
Schedule of Common Equity [Line Items] |
Common Equity | COMMON EQUITY Common Stock Split - On April 20, 2016, Alliant Energy’s Board of Directors approved a two-for-one common stock split and a proportionate increase in the number of authorized shares of common stock of Alliant Energy from 240 million shares to 480 million shares to implement the stock split. Alliant Energy shareowners of record at the close of business on May 4, 2016 received one additional share of Alliant Energy common stock for each share held on that date. The proportionate interest that a shareowner owns in Alliant Energy did not change as a result of the stock split. The additional shares were distributed on May 19, 2016 and post-split trading began on May 20, 2016. All Alliant Energy share and per share amounts in this report have been reflected on a post-split basis. Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:
| 2016 |  | 2015 |  | 2014
Shares outstanding, January 1 | 226,918,432 |  |  | 221,871,360 |  |  | 221,887,338 |
At-the-market offering program | — |  |  | 4,373,234 |  |  | — |
Shareowner Direct Plan issuances | 732,814 |  |  | 606,010 |  |  | — |
Equity-based compensation plans (Note 12(b)) | 22,408 |  |  | 112,756 |  |  | 71,094 |
Other | — |  |  | (44,928 | ) |  | (87,072 | )
Shares outstanding, December 31 | 227,673,654 |  |  | 226,918,432 |  |  | 221,871,360 |
At December 31, 2016, Alliant Energy had a total of 11.3 million shares available for issuance in the aggregate, pursuant to its Amended and Restated OIP, Shareowner Direct Plan and 401(k) Savings Plan. At-the-Market Offering Program - In 2015, Alliant Energy filed a prospectus supplement under which it may sell up to $150 million of its common stock through an at-the-market offering program. In 2015, Alliant Energy issued 4,373,234 shares of common stock through this program and received cash proceeds of $133 million, net of $2 million in fees and commissions. The proceeds from the issuances of common stock were used for general corporate purposes. This at-the-market offering program expired in 2016. Shareowner Direct Plan - Beginning in 2015, Alliant Energy satisfied its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market. Shareowner Rights Agreement - Alliant Energy has established an amended and restated Shareowner Rights Agreement. The rights under this agreement will only become exercisable if a person or group has acquired, or announced an intention to acquire, 15% or more of Alliant Energy’s outstanding common stock. Each right will initially entitle registered shareowners to purchase from Alliant Energy one-quarter of one share of Alliant Energy’s common stock. The rights will be exercisable at an initial price of $55.00 per full share, subject to adjustment. If any shareowner acquires 15% or more of the outstanding common stock of Alliant Energy, each right (subject to limitations) will entitle its holder to purchase, at the right’s then current exercise price, a number of common shares of Alliant Energy or of the acquirer having a market value at the time of twice the right’s per full share exercise price. Alliant Energy’s Board of Directors is authorized to reduce the 15% ownership threshold to not less than 10%. The amended and restated Shareowner Rights Agreement expires in December 2018. Alliant Energy currently has no intention to redeem the Shareowner Rights Agreement and plans to allow it to naturally expire at the end of the term. Dividend Restrictions - Alliant Energy does not have any significant common stock dividend restrictions. IPL and WPL each have common stock dividend restrictions based on applicable regulatory limitations. IPL also has common stock dividend restrictions based on the terms of its outstanding preferred stock. As of December 31, 2016, IPL and WPL were in compliance with all such dividend restrictions. IPL is restricted from paying common stock dividends to its parent company, Alliant Energy, if for any past or current dividend period, dividends on its preferred stock have not been paid, or declared and set apart for payment. IPL has paid all dividends on its preferred stock through 2016. Under the Federal Power Act, IPL may not pay dividends to its parent company in excess of the current amount of its retained earnings. As of December 31, 2016, IPL’s amount of retained earnings that were free of dividend restrictions was $618 million. If IPL’s actual 13-month average common equity ratio (calculated on a financial basis consistent with IPL’s rate cases) falls below 42% of total capitalization, IPL is required to notify the IUB. Pursuant to a December 2016 PSCW order, WPL has a regulatory limitation on distributions to its parent company. WPL is prohibited from paying annual common stock dividends to its parent company in excess of forecasted dividend levels of $126 million in 2017 and $140 million in 2018 if WPL’s actual 13-month average common equity ratio (calculated on a financial basis consistent with WPL’s rate cases) would fall below 51.00% for 2017 or 2018. As of December 31, 2016, WPL’s amount of retained earnings that were free of dividend restrictions was $126 million for 2017. Restricted Net Assets of Subsidiaries - IPL and WPL do not have regulatory authority to lend or advance any amounts to their parent company. As of December 31, 2016, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company, Alliant Energy, in the form of loans, advances or cash dividends without the consent of IPL’s and WPL’s regulatory authorities was $1.6 billion for each. Comprehensive Income - In 2016, 2015 and 2014, Alliant Energy’s other comprehensive income (loss) was $0, $0.2 million and ($0.4) million, respectively; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. In 2016, 2015 and 2014, IPL and WPL had no other comprehensive income; therefore their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.

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