XML 47 R14.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Common Equity | 12 Months Ended
--- | ---
Dec. 31, 2018
Schedule of Common Equity [Line Items] |
Common Equity | COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:
| 2018 |  | 2017 |  | 2016
Shares outstanding, January 1 | 231,348,646 |  |  | 227,673,654 |  |  | 226,918,432 |
At-the-market offering programs | 4,171,013 |  |  | 3,074,931 |  |  | — |
Shareowner Direct Plan issuances | 576,965 |  |  | 640,723 |  |  | 732,814 |
Equity-based compensation plans (Note 13(b)) | 5,078 |  |  | 5,185 |  |  | 22,408 |
Other | (38,423 | ) |  | (45,847 | ) |  | — |
Shares outstanding, December 31 | 236,063,279 |  |  | 231,348,646 |  |  | 227,673,654 |
At December 31, 2018, Alliant Energy had a total of 11.2 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 Programs - In 2018 and 2017, Alliant Energy filed prospectus supplements under which it could sell up to $175 million and $125 million of its common stock, respectively, through at-the-market offering programs. In 2018, Alliant Energy issued 4,171,013 shares of common stock through this program and received cash proceeds of $173 million, net of $2 million in commissions and fees. In 2017, Alliant Energy issued 3,074,931 shares of common stock through this program and received cash proceeds of $124 million, net of $1 million in commissions and fees. The 2017 at-the-market offering program expired in 2018, and Alliant Energy currently has no plans to issue any additional common stock through the 2018 at-the-market offering program. Shareowner Direct Plan - Alliant Energy satisfies 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. Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. In the forward sale transaction, the counterparties, or their affiliates, borrowed an aggregate of 8,358,973 shares of Alliant Energy common stock from third parties and sold such shares to the related underwriters. Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Alliant Energy has not yet received any proceeds from the offering and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy expects to settle the forward sale agreements prior to December 31, 2019 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. The initial forward sale price of $44.33 per share, is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreement. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. As of December 31, 2018, the securities under the forward sale agreements were excluded from the calculation of diluted EPS as they were antidilutive. Shareowner Rights Agreement - Alliant Energy previously established an amended and restated Shareowner Rights Agreement. The rights under this agreement were exercisable if a person or group acquired, or announced an intention to acquire, 15% or more of Alliant Energy’s outstanding common stock. In January 2018, Alliant Energy’s Board of Directors authorized the redemption of the rights, which were redeemed to shareowners as of the close of business on January 31, 2018. Comprehensive Income (Loss) - In 2018, 2017 and 2016, Alliant Energy’s other comprehensive income (loss) was $2.2 million, ($0.1) million and $0 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 2018, 2017 and 2016, 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 Share Activity - A summary of Alliant Energy’s common stock activity was as follows:
| 2018 |  | 2017 |  | 2016
Shares outstanding, January 1 | 231,348,646 |  |  | 227,673,654 |  |  | 226,918,432 |
At-the-market offering programs | 4,171,013 |  |  | 3,074,931 |  |  | — |
Shareowner Direct Plan issuances | 576,965 |  |  | 640,723 |  |  | 732,814 |
Equity-based compensation plans (Note 13(b)) | 5,078 |  |  | 5,185 |  |  | 22,408 |
Other | (38,423 | ) |  | (45,847 | ) |  | — |
Shares outstanding, December 31 | 236,063,279 |  |  | 231,348,646 |  |  | 227,673,654 |
At December 31, 2018, Alliant Energy had a total of 11.2 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 Programs - In 2018 and 2017, Alliant Energy filed prospectus supplements under which it could sell up to $175 million and $125 million of its common stock, respectively, through at-the-market offering programs. In 2018, Alliant Energy issued 4,171,013 shares of common stock through this program and received cash proceeds of $173 million, net of $2 million in commissions and fees. In 2017, Alliant Energy issued 3,074,931 shares of common stock through this program and received cash proceeds of $124 million, net of $1 million in commissions and fees. The 2017 at-the-market offering program expired in 2018, and Alliant Energy currently has no plans to issue any additional common stock through the 2018 at-the-market offering program. Shareowner Direct Plan - Alliant Energy satisfies 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. Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. In the forward sale transaction, the counterparties, or their affiliates, borrowed an aggregate of 8,358,973 shares of Alliant Energy common stock from third parties and sold such shares to the related underwriters. Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Alliant Energy has not yet received any proceeds from the offering and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy expects to settle the forward sale agreements prior to December 31, 2019 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. The initial forward sale price of $44.33 per share, is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreement. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. As of December 31, 2018, the securities under the forward sale agreements were excluded from the calculation of diluted EPS as they were antidilutive. Shareowner Rights Agreement - Alliant Energy previously established an amended and restated Shareowner Rights Agreement. The rights under this agreement were exercisable if a person or group acquired, or announced an intention to acquire, 15% or more of Alliant Energy’s outstanding common stock. In January 2018, Alliant Energy’s Board of Directors authorized the redemption of the rights, which were redeemed to shareowners as of the close of business on January 31, 2018. Comprehensive Income (Loss) - In 2018, 2017 and 2016, Alliant Energy’s other comprehensive income (loss) was $2.2 million, ($0.1) million and $0 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 2018, 2017 and 2016, 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 Share Activity - A summary of Alliant Energy’s common stock activity was as follows:
| 2018 |  | 2017 |  | 2016
Shares outstanding, January 1 | 231,348,646 |  |  | 227,673,654 |  |  | 226,918,432 |
At-the-market offering programs | 4,171,013 |  |  | 3,074,931 |  |  | — |
Shareowner Direct Plan issuances | 576,965 |  |  | 640,723 |  |  | 732,814 |
Equity-based compensation plans (Note 13(b)) | 5,078 |  |  | 5,185 |  |  | 22,408 |
Other | (38,423 | ) |  | (45,847 | ) |  | — |
Shares outstanding, December 31 | 236,063,279 |  |  | 231,348,646 |  |  | 227,673,654 |
At December 31, 2018, Alliant Energy had a total of 11.2 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 Programs - In 2018 and 2017, Alliant Energy filed prospectus supplements under which it could sell up to $175 million and $125 million of its common stock, respectively, through at-the-market offering programs. In 2018, Alliant Energy issued 4,171,013 shares of common stock through this program and received cash proceeds of $173 million, net of $2 million in commissions and fees. In 2017, Alliant Energy issued 3,074,931 shares of common stock through this program and received cash proceeds of $124 million, net of $1 million in commissions and fees. The 2017 at-the-market offering program expired in 2018, and Alliant Energy currently has no plans to issue any additional common stock through the 2018 at-the-market offering program. Shareowner Direct Plan - Alliant Energy satisfies 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. Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. In the forward sale transaction, the counterparties, or their affiliates, borrowed an aggregate of 8,358,973 shares of Alliant Energy common stock from third parties and sold such shares to the related underwriters. Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Alliant Energy has not yet received any proceeds from the offering and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy expects to settle the forward sale agreements prior to December 31, 2019 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. The initial forward sale price of $44.33 per share, is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreement. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. As of December 31, 2018, the securities under the forward sale agreements were excluded from the calculation of diluted EPS as they were antidilutive. Shareowner Rights Agreement - Alliant Energy previously established an amended and restated Shareowner Rights Agreement. The rights under this agreement were exercisable if a person or group acquired, or announced an intention to acquire, 15% or more of Alliant Energy’s outstanding common stock. In January 2018, Alliant Energy’s Board of Directors authorized the redemption of the rights, which were redeemed to shareowners as of the close of business on January 31, 2018. Comprehensive Income (Loss) - In 2018, 2017 and 2016, Alliant Energy’s other comprehensive income (loss) was $2.2 million, ($0.1) million and $0 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 2018, 2017 and 2016, 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.

X
- Definition [Line Items] for Schedule of Common Equity [Table] + References No definition available. + Details
Name: | lnt_ScheduleOfCommonEquityLineItems
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -URI http://asc.fasb.org/topic&trid=2208762 + Details
Name: | us-gaap_StockholdersEquityNoteDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |