Summary Of Significant Accounting Policies	6 Months Ended
Summary Of Significant Accounting Policies	Jun. 30, 2018
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 six months ended June 30, 2018 are not necessarily indicative of results that may be expected for the year ending December 31, 2018. 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, including modifications to the presentation of the components of net periodic benefit costs for defined benefit pension and other postretirement plans in the income statements as discussed in Note 1(d), restricted cash and cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d), and segment reporting as discussed in Note 14. Discontinued operations reported in Alliant Energy’s income statements is related to various warranty claims associated with the sale of RMT, Inc. in 2013, which have resulted in operating expenses and income subsequent to the sale. NOTE 1(b) Cash, Cash Equivalents and Restricted Cash - At June 30, 2018 and December 31, 2017, restricted cash primarily related to deposits with trustees and borrowing requirements in Sheboygan Power, LLC’s debt agreement. Refer to Note 1(d) for discussion of revisions to the cash flows statements to include immaterial restricted cash amounts. NOTE 1(c) Revenue Recognition - Utility - Revenues from Alliant Energy’s utility business are primarily from retail and wholesale electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the date of each customer’s last meter reading. The unbilled revenue is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of June 30, 2018, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Transportation business and are recognized over time as services are rendered or goods are delivered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for goods delivered or services performed. NOTE 1(d) 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. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018 using the modified retrospective method of adoption, which was applied to contracts with customers that were completed subsequent to January 1, 2018. Alliant Energy, IPL and WPL utilized a portfolio approach upon adoption, which involved evaluating portfolios of contracts with similar characteristics, where the effects of applying the standard were not expected to be materially different than evaluating on an individual contract basis. Upon adoption, there were no cumulative effect adjustments made to the January 1, 2018 retained earnings balances. In addition, prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Alliant Energy, IPL and WPL did not have a material change in revenue recognition, including the timing and pattern of revenue recognition, as a result of the adoption of this standard. Refer to Notes 1(c) and 8 for further discussion of revenue recognition. 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. Only the service cost component of net periodic benefit costs is eligible for capitalization into property, plant and equipment; however, IPL and WPL, as rate-regulated entities, capitalize the other components of net periodic benefit costs into regulatory assets or regulatory liabilities. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018 and used the retrospective method of adoption for the presentation requirements and prospective method of adoption for the capitalization requirements. Alliant Energy, IPL and WPL used the actual net periodic benefit costs adjusted for approximately 40% of net periodic benefit costs allocated to capital projects for the retrospective method of adoption for the presentation requirements. The change in presentation resulted in a decrease in “Other operation and maintenance” expenses and an increase in “Other (income) and deductions” in Alliant Energy’s, IPL’s and WPL’s income statements of $4.4 million, $1.8 million and $2.5 million for the three months ended June 30, 2017, and $8.7 million, $3.5 million and $5.1 million for the six months ended June 30, 2017, respectively. Cash Flows Statements - In August 2016, the Financial Accounting Standards Board issued an accounting standard providing specific guidance on several cash flow classification matters. The accounting standard requires classification of the consideration received for the beneficial interest obtained for transferring accounts receivable from IPL’s sales of accounts receivable program as an investing activity, instead of an operating activity. Alliant Energy, IPL and WPL retrospectively adopted this standard on January 1, 2018, using a method that allocates cash flows between operating and investing activities based on monthly transactional activity. If the methodology was based on a method other than monthly, it may result in a different reclassification between operating and investing cash flows. For the six months ended June 30, 2017, Alliant Energy and IPL reclassified $374.5 million of the related cash received from IPL’s sales of accounts receivable program from operating activities to investing activities. The related impact on Alliant Energy’s and IPL’s cash flows statements for the year ended December 31, 2017 was $681.9 million. In November 2016, the Financial Accounting Standards Board issued an accounting standard requiring restricted cash to be included within beginning-of-period and end-of-period cash and cash equivalents in the cash flows statements. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018, which was applied retrospectively. Refer to Note 1(b) for further discussion of restricted cash.
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 six months ended June 30, 2018 are not necessarily indicative of results that may be expected for the year ending December 31, 2018. 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, including modifications to the presentation of the components of net periodic benefit costs for defined benefit pension and other postretirement plans in the income statements as discussed in Note 1(d), restricted cash and cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d), and segment reporting as discussed in Note 14. Discontinued operations reported in Alliant Energy’s income statements is related to various warranty claims associated with the sale of RMT, Inc. in 2013, which have resulted in operating expenses and income subsequent to the sale. NOTE 1(b) Cash, Cash Equivalents and Restricted Cash - At June 30, 2018 and December 31, 2017, restricted cash primarily related to deposits with trustees and borrowing requirements in Sheboygan Power, LLC’s debt agreement. Refer to Note 1(d) for discussion of revisions to the cash flows statements to include immaterial restricted cash amounts. NOTE 1(c) Revenue Recognition - Utility - Revenues from Alliant Energy’s utility business are primarily from retail and wholesale electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the date of each customer’s last meter reading. The unbilled revenue is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of June 30, 2018, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Transportation business and are recognized over time as services are rendered or goods are delivered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for goods delivered or services performed. NOTE 1(d) 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. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018 using the modified retrospective method of adoption, which was applied to contracts with customers that were completed subsequent to January 1, 2018. Alliant Energy, IPL and WPL utilized a portfolio approach upon adoption, which involved evaluating portfolios of contracts with similar characteristics, where the effects of applying the standard were not expected to be materially different than evaluating on an individual contract basis. Upon adoption, there were no cumulative effect adjustments made to the January 1, 2018 retained earnings balances. In addition, prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Alliant Energy, IPL and WPL did not have a material change in revenue recognition, including the timing and pattern of revenue recognition, as a result of the adoption of this standard. Refer to Notes 1(c) and 8 for further discussion of revenue recognition. 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. Only the service cost component of net periodic benefit costs is eligible for capitalization into property, plant and equipment; however, IPL and WPL, as rate-regulated entities, capitalize the other components of net periodic benefit costs into regulatory assets or regulatory liabilities. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018 and used the retrospective method of adoption for the presentation requirements and prospective method of adoption for the capitalization requirements. Alliant Energy, IPL and WPL used the actual net periodic benefit costs adjusted for approximately 40% of net periodic benefit costs allocated to capital projects for the retrospective method of adoption for the presentation requirements. The change in presentation resulted in a decrease in “Other operation and maintenance” expenses and an increase in “Other (income) and deductions” in Alliant Energy’s, IPL’s and WPL’s income statements of $4.4 million, $1.8 million and $2.5 million for the three months ended June 30, 2017, and $8.7 million, $3.5 million and $5.1 million for the six months ended June 30, 2017, respectively. Cash Flows Statements - In August 2016, the Financial Accounting Standards Board issued an accounting standard providing specific guidance on several cash flow classification matters. The accounting standard requires classification of the consideration received for the beneficial interest obtained for transferring accounts receivable from IPL’s sales of accounts receivable program as an investing activity, instead of an operating activity. Alliant Energy, IPL and WPL retrospectively adopted this standard on January 1, 2018, using a method that allocates cash flows between operating and investing activities based on monthly transactional activity. If the methodology was based on a method other than monthly, it may result in a different reclassification between operating and investing cash flows. For the six months ended June 30, 2017, Alliant Energy and IPL reclassified $374.5 million of the related cash received from IPL’s sales of accounts receivable program from operating activities to investing activities. The related impact on Alliant Energy’s and IPL’s cash flows statements for the year ended December 31, 2017 was $681.9 million. In November 2016, the Financial Accounting Standards Board issued an accounting standard requiring restricted cash to be included within beginning-of-period and end-of-period cash and cash equivalents in the cash flows statements. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018, which was applied retrospectively. Refer to Note 1(b) for further discussion of restricted cash.
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 six months ended June 30, 2018 are not necessarily indicative of results that may be expected for the year ending December 31, 2018. 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, including modifications to the presentation of the components of net periodic benefit costs for defined benefit pension and other postretirement plans in the income statements as discussed in Note 1(d), restricted cash and cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d), and segment reporting as discussed in Note 14. Discontinued operations reported in Alliant Energy’s income statements is related to various warranty claims associated with the sale of RMT, Inc. in 2013, which have resulted in operating expenses and income subsequent to the sale. NOTE 1(b) Cash, Cash Equivalents and Restricted Cash - At June 30, 2018 and December 31, 2017, restricted cash primarily related to deposits with trustees and borrowing requirements in Sheboygan Power, LLC’s debt agreement. Refer to Note 1(d) for discussion of revisions to the cash flows statements to include immaterial restricted cash amounts. NOTE 1(c) Revenue Recognition - Utility - Revenues from Alliant Energy’s utility business are primarily from retail and wholesale electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the date of each customer’s last meter reading. The unbilled revenue is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of June 30, 2018, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Transportation business and are recognized over time as services are rendered or goods are delivered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for goods delivered or services performed. NOTE 1(d) 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. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018 using the modified retrospective method of adoption, which was applied to contracts with customers that were completed subsequent to January 1, 2018. Alliant Energy, IPL and WPL utilized a portfolio approach upon adoption, which involved evaluating portfolios of contracts with similar characteristics, where the effects of applying the standard were not expected to be materially different than evaluating on an individual contract basis. Upon adoption, there were no cumulative effect adjustments made to the January 1, 2018 retained earnings balances. In addition, prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Alliant Energy, IPL and WPL did not have a material change in revenue recognition, including the timing and pattern of revenue recognition, as a result of the adoption of this standard. Refer to Notes 1(c) and 8 for further discussion of revenue recognition. 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. Only the service cost component of net periodic benefit costs is eligible for capitalization into property, plant and equipment; however, IPL and WPL, as rate-regulated entities, capitalize the other components of net periodic benefit costs into regulatory assets or regulatory liabilities. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018 and used the retrospective method of adoption for the presentation requirements and prospective method of adoption for the capitalization requirements. Alliant Energy, IPL and WPL used the actual net periodic benefit costs adjusted for approximately 40% of net periodic benefit costs allocated to capital projects for the retrospective method of adoption for the presentation requirements. The change in presentation resulted in a decrease in “Other operation and maintenance” expenses and an increase in “Other (income) and deductions” in Alliant Energy’s, IPL’s and WPL’s income statements of $4.4 million, $1.8 million and $2.5 million for the three months ended June 30, 2017, and $8.7 million, $3.5 million and $5.1 million for the six months ended June 30, 2017, respectively. Cash Flows Statements - In August 2016, the Financial Accounting Standards Board issued an accounting standard providing specific guidance on several cash flow classification matters. The accounting standard requires classification of the consideration received for the beneficial interest obtained for transferring accounts receivable from IPL’s sales of accounts receivable program as an investing activity, instead of an operating activity. Alliant Energy, IPL and WPL retrospectively adopted this standard on January 1, 2018, using a method that allocates cash flows between operating and investing activities based on monthly transactional activity. If the methodology was based on a method other than monthly, it may result in a different reclassification between operating and investing cash flows. For the six months ended June 30, 2017, Alliant Energy and IPL reclassified $374.5 million of the related cash received from IPL’s sales of accounts receivable program from operating activities to investing activities. The related impact on Alliant Energy’s and IPL’s cash flows statements for the year ended December 31, 2017 was $681.9 million. In November 2016, the Financial Accounting Standards Board issued an accounting standard requiring restricted cash to be included within beginning-of-period and end-of-period cash and cash equivalents in the cash flows statements. Alliant Energy, IPL and WPL adopted this standard on January 1, 2018, which was applied retrospectively. Refer to Note 1(b) for further discussion of restricted cash.