Summary Of Significant Accounting Policies	9 Months Ended
Summary Of Significant Accounting Policies	Sep. 30, 2017
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K. In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2017 are not necessarily indicative of results that may be expected for the year ending December 31, 2017. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Discontinued operations reported in Alliant Energy’s income statements is related to various warranty claims associated with the sale of RMT in 2013, which have resulted in operating expenses and income subsequent to the sale. NOTE 1(b) New Accounting Standards - Revenue Recognition - In May 2014, the Financial Accounting Standards Board issued an accounting standard providing principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. This standard also requires disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2018 and currently expect to use the modified retrospective method of adoption. If applicable, this method requires a cumulative-effect adjustment to the opening retained earnings balance on January 1, 2018, as if the standard had always been in effect. Alliant Energy, IPL and WPL have continued to make progress in the evaluation of the revenue recognition standard and do not currently anticipate a significant change in revenue recognition for retail electric and gas sales. These sales represent the majority of Alliant Energy’s, IPL’s and WPL’s revenues and are from tariff offerings that provide electricity or natural gas without a defined contractual term. For such arrangements, revenues from contracts with customers will be equivalent to the electricity or natural gas supplied and billed, or estimated to be billed, and there will be no significant shift in the timing or pattern of revenue recognition for such sales. The most significant impact to the financial statements for Alliant Energy, IPL and WPL is expected to be in the form of additional disclosures. The incremental disclosures could include disaggregation of revenue by location and customer class. Alliant Energy, IPL and WPL expect to complete the evaluation of the impact of the revenue recognition standard on their financial condition, results of operations and disclosures by January 1, 2018. Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet for all leases with terms longer than 12 months. The standard also requires disclosure of key information about leasing arrangements. Alliant Energy, IPL and WPL currently expect to adopt this standard on January 1, 2019 and are evaluating the impact of this standard on their financial condition and results of operations and expect an increase in assets and liabilities from recognizing operating leases on their balance sheets. Presentation of Net Periodic Pension and Postretirement Benefit Costs - In March 2017, the Financial Accounting Standards Board issued an accounting standard amending the income statement presentation of the components of net periodic benefit costs for defined benefit pension and other postretirement plans. The standard requires entities to (1) disaggregate the current service cost component from the other components of net periodic benefit costs and present it with other employee compensation costs in the income statement; and (2) include the other components in the income statement outside of operating income. This new presentation will shift the majority of the net periodic benefit costs from “Other operation and maintenance” expenses to “Interest expense and other” expenses in the income statements. In addition, only the service cost component of net periodic benefit costs is eligible for capitalization into property, plant and equipment, when applicable. IPL and WPL, as rate-regulated entities, currently expect to capitalize the other components of net periodic benefit costs into regulatory assets or regulatory liabilities. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2018. Upon adoption, the standard must be applied retrospectively for the presentation requirements and prospectively for the capitalization requirements. Alliant Energy, IPL and WPL continue to evaluate additional impacts of this standard on their financial condition and results of operations.
IPL [Member]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K. In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2017 are not necessarily indicative of results that may be expected for the year ending December 31, 2017. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Discontinued operations reported in Alliant Energy’s income statements is related to various warranty claims associated with the sale of RMT in 2013, which have resulted in operating expenses and income subsequent to the sale. NOTE 1(b) New Accounting Standards - Revenue Recognition - In May 2014, the Financial Accounting Standards Board issued an accounting standard providing principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. This standard also requires disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2018 and currently expect to use the modified retrospective method of adoption. If applicable, this method requires a cumulative-effect adjustment to the opening retained earnings balance on January 1, 2018, as if the standard had always been in effect. Alliant Energy, IPL and WPL have continued to make progress in the evaluation of the revenue recognition standard and do not currently anticipate a significant change in revenue recognition for retail electric and gas sales. These sales represent the majority of Alliant Energy’s, IPL’s and WPL’s revenues and are from tariff offerings that provide electricity or natural gas without a defined contractual term. For such arrangements, revenues from contracts with customers will be equivalent to the electricity or natural gas supplied and billed, or estimated to be billed, and there will be no significant shift in the timing or pattern of revenue recognition for such sales. The most significant impact to the financial statements for Alliant Energy, IPL and WPL is expected to be in the form of additional disclosures. The incremental disclosures could include disaggregation of revenue by location and customer class. Alliant Energy, IPL and WPL expect to complete the evaluation of the impact of the revenue recognition standard on their financial condition, results of operations and disclosures by January 1, 2018. Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet for all leases with terms longer than 12 months. The standard also requires disclosure of key information about leasing arrangements. Alliant Energy, IPL and WPL currently expect to adopt this standard on January 1, 2019 and are evaluating the impact of this standard on their financial condition and results of operations and expect an increase in assets and liabilities from recognizing operating leases on their balance sheets. Presentation of Net Periodic Pension and Postretirement Benefit Costs - In March 2017, the Financial Accounting Standards Board issued an accounting standard amending the income statement presentation of the components of net periodic benefit costs for defined benefit pension and other postretirement plans. The standard requires entities to (1) disaggregate the current service cost component from the other components of net periodic benefit costs and present it with other employee compensation costs in the income statement; and (2) include the other components in the income statement outside of operating income. This new presentation will shift the majority of the net periodic benefit costs from “Other operation and maintenance” expenses to “Interest expense and other” expenses in the income statements. In addition, only the service cost component of net periodic benefit costs is eligible for capitalization into property, plant and equipment, when applicable. IPL and WPL, as rate-regulated entities, currently expect to capitalize the other components of net periodic benefit costs into regulatory assets or regulatory liabilities. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2018. Upon adoption, the standard must be applied retrospectively for the presentation requirements and prospectively for the capitalization requirements. Alliant Energy, IPL and WPL continue to evaluate additional impacts of this standard on their financial condition and results of operations.
WPL [Member]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K. In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2017 are not necessarily indicative of results that may be expected for the year ending December 31, 2017. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Discontinued operations reported in Alliant Energy’s income statements is related to various warranty claims associated with the sale of RMT in 2013, which have resulted in operating expenses and income subsequent to the sale. NOTE 1(b) New Accounting Standards - Revenue Recognition - In May 2014, the Financial Accounting Standards Board issued an accounting standard providing principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. This standard also requires disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2018 and currently expect to use the modified retrospective method of adoption. If applicable, this method requires a cumulative-effect adjustment to the opening retained earnings balance on January 1, 2018, as if the standard had always been in effect. Alliant Energy, IPL and WPL have continued to make progress in the evaluation of the revenue recognition standard and do not currently anticipate a significant change in revenue recognition for retail electric and gas sales. These sales represent the majority of Alliant Energy’s, IPL’s and WPL’s revenues and are from tariff offerings that provide electricity or natural gas without a defined contractual term. For such arrangements, revenues from contracts with customers will be equivalent to the electricity or natural gas supplied and billed, or estimated to be billed, and there will be no significant shift in the timing or pattern of revenue recognition for such sales. The most significant impact to the financial statements for Alliant Energy, IPL and WPL is expected to be in the form of additional disclosures. The incremental disclosures could include disaggregation of revenue by location and customer class. Alliant Energy, IPL and WPL expect to complete the evaluation of the impact of the revenue recognition standard on their financial condition, results of operations and disclosures by January 1, 2018. Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet for all leases with terms longer than 12 months. The standard also requires disclosure of key information about leasing arrangements. Alliant Energy, IPL and WPL currently expect to adopt this standard on January 1, 2019 and are evaluating the impact of this standard on their financial condition and results of operations and expect an increase in assets and liabilities from recognizing operating leases on their balance sheets. Presentation of Net Periodic Pension and Postretirement Benefit Costs - In March 2017, the Financial Accounting Standards Board issued an accounting standard amending the income statement presentation of the components of net periodic benefit costs for defined benefit pension and other postretirement plans. The standard requires entities to (1) disaggregate the current service cost component from the other components of net periodic benefit costs and present it with other employee compensation costs in the income statement; and (2) include the other components in the income statement outside of operating income. This new presentation will shift the majority of the net periodic benefit costs from “Other operation and maintenance” expenses to “Interest expense and other” expenses in the income statements. In addition, only the service cost component of net periodic benefit costs is eligible for capitalization into property, plant and equipment, when applicable. IPL and WPL, as rate-regulated entities, currently expect to capitalize the other components of net periodic benefit costs into regulatory assets or regulatory liabilities. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2018. Upon adoption, the standard must be applied retrospectively for the presentation requirements and prospectively for the capitalization requirements. Alliant Energy, IPL and WPL continue to evaluate additional impacts of this standard on their financial condition and results of operations.