XML 58 R24.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Segments Of Business | 12 Months Ended
--- | ---
Dec. 31, 2017
Segment Reporting Information [Line Items] |
Segments Of Business | SEGMENTS OF BUSINESS In the fourth quarter of 2017, Alliant Energy and WPL modified the segment reporting related to their ATC Investment, consistent with information used by their chief operating decision maker to evaluate performance and allocate resources. As of December 31, 2017, the ATC Investment is no longer included in Alliant Energy’s utility electric operations reportable segment or WPL’s electric operations reportable segment. As a result, all prior period amounts impacted by this change were reclassified to conform to the new presentation. Alliant Energy’s related amounts were reclassified from “Electric Utility” to “ATC Investment, Non-Utility, Parent and Other.” WPL’s related amounts were reclassified from “Electric” to “Other.” Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2017 are:
• | Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.”
• | ATC Investment, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s ATC Investment, Transportation, a non-utility wind investment, the Sheboygan Falls Energy Facility and other non-utility investments, which are described in Note 1(a).
Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2017 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,894.7 |  |  |  | $400.9 |  |  |  | $47.5 |  |  |  | $3,343.1 |  |  |  | $39.1 |  |  |  | $3,382.2 |
Depreciation and amortization | 412.0 |  |  | 38.2 |  |  | 7.7 |  |  | 457.9 |  |  | 3.9 |  |  | 461.8 |
Operating income (loss) | 586.5 |  |  | 45.3 |  |  | (11.7 | ) |  | 620.1 |  |  | 33.3 |  |  | 653.4 |
Interest expense |  |  |  |  |  |  | 206.2 |  |  | 9.4 |  |  | 215.6 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (44.1 | ) |  | (44.8 | )
Income taxes |  |  |  |  |  |  | 51.0 |  |  | 15.7 |  |  | 66.7 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 403.4 |  |  | 53.9 |  |  | 457.3 |
Total assets | 11,396.2 |  |  | 1,199.8 |  |  | 766.5 |  |  | 13,362.5 |  |  | 825.3 |  |  | 14,187.8 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |  |  | 373.1 |  |  | 381.4 |
Construction and acquisition expenditures | 1,154.9 |  |  | 125.2 |  |  | 1.7 |  |  | 1,281.8 |  |  | 185.1 |  |  | 1,466.9 |
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2016 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,875.5 |  |  |  | $355.4 |  |  |  | $48.6 |  |  |  | $3,279.5 |  |  |  | $40.5 |  |  |  | $3,320.0 |
Depreciation and amortization | 367.0 |  |  | 34.2 |  |  | 2.1 |  |  | 403.3 |  |  | 8.3 |  |  | 411.6 |
Operating income (loss) | 571.9 |  |  | 30.7 |  |  | (4.8 | ) |  | 597.8 |  |  | (60.8 | ) |  | 537.0 |
Interest expense |  |  |  |  |  |  | 194.6 |  |  | 1.6 |  |  | 196.2 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (38.9 | ) |  | (39.6 | )
Income tax expense (benefit) |  |  |  |  |  |  | 71.4 |  |  | (12.0 | ) |  | 59.4 |
Net income (loss) attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 385.2 |  |  | (13.7 | ) |  | 371.5 |
Total assets | 10,722.9 |  |  | 1,091.1 |  |  | 781.0 |  |  | 12,595.0 |  |  | 778.8 |  |  | 13,373.8 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |  |  | 318.3 |  |  | 326.0 |
Construction and acquisition expenditures | 994.0 |  |  | 137.1 |  |  | 0.1 |  |  | 1,131.2 |  |  | 65.6 |  |  | 1,196.8 |
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2015 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,770.5 |  |  |  | $381.2 |  |  |  | $57.9 |  |  |  | $3,209.6 |  |  |  | $44.0 |  |  |  | $3,253.6 |
Depreciation and amortization | 358.6 |  |  | 31.1 |  |  | 1.8 |  |  | 391.5 |  |  | 9.8 |  |  | 401.3 |
Operating income | 514.1 |  |  | 34.6 |  |  | 1.9 |  |  | 550.6 |  |  | 26.4 |  |  | 577.0 |
Interest expense |  |  |  |  |  |  | 189.2 |  |  | (2.1 | ) |  | 187.1 |
Equity income from unconsolidated investments, net | (0.9 | ) |  | — |  |  | — |  |  | (0.9 | ) |  | (32.9 | ) |  | (33.8 | )
Income taxes |  |  |  |  |  |  | 46.2 |  |  | 24.2 |  |  | 70.4 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 343.4 |  |  | 34.8 |  |  | 378.2 |
Total assets | 9,918.0 |  |  | 939.3 |  |  | 828.9 |  |  | 11,686.2 |  |  | 809.0 |  |  | 12,495.2 |
Investments in equity method subsidiaries | 8.7 |  |  | — |  |  | — |  |  | 8.7 |  |  | 294.2 |  |  | 302.9 |
Construction and acquisition expenditures | 852.5 |  |  | 106.4 |  |  | 1.4 |  |  | 960.3 |  |  | 74.0 |  |  | 1,034.3 |
IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2017 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,598.9 |  |  |  | $226.0 |  |  |  | $45.4 |  |  |  | $1,870.3 |
Depreciation and amortization | 215.1 |  |  | 22.2 |  |  | 7.7 |  |  | 245.0 |
Operating income (loss) | 281.1 |  |  | 20.8 |  |  | (5.0 | ) |  | 296.9 |
Interest expense |  |  |  |  |  |  | 112.4 |
Income tax benefit |  |  |  |  |  |  | (10.9 | )
Earnings available for common stock |  |  |  |  |  |  | 216.8 |
Total assets | 6,524.4 |  |  | 727.9 |  |  | 353.7 |  |  | 7,606.0 |
Construction and acquisition expenditures | 594.1 |  |  | 80.7 |  |  | 1.2 |  |  | 676.0 |
2016 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,569.7 |  |  |  | $204.0 |  |  |  | $46.7 |  |  |  | $1,820.4 |
Depreciation and amortization | 189.4 |  |  | 19.3 |  |  | 2.1 |  |  | 210.8 |
Operating income | 252.0 |  |  | 15.5 |  |  | 3.3 |  |  | 270.8 |
Interest expense |  |  |  |  |  |  | 103.2 |
Income tax benefit |  |  |  |  |  |  | (5.9 | )
Earnings available for common stock |  |  |  |  |  |  | 215.6 |
Total assets | 6,278.2 |  |  | 653.3 |  |  | 373.2 |  |  | 7,304.7 |
Construction and acquisition expenditures | 598.1 |  |  | 91.5 |  |  | 0.1 |  |  | 689.7 |
2015 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,503.8 |  |  |  | $217.3 |  |  |  | $53.4 |  |  |  | $1,774.5 |
Depreciation and amortization | 187.9 |  |  | 17.5 |  |  | 1.8 |  |  | 207.2 |
Operating income | 218.8 |  |  | 17.7 |  |  | 5.4 |  |  | 241.9 |
Interest expense |  |  |  |  |  |  | 96.8 |
Income tax benefit |  |  |  |  |  |  | (22.7 | )
Earnings available for common stock |  |  |  |  |  |  | 186.0 |
Total assets | 5,754.1 |  |  | 548.2 |  |  | 406.8 |  |  | 6,709.1 |
Construction and acquisition expenditures | 561.2 |  |  | 56.7 |  |  | 1.4 |  |  | 619.3 |
WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes WPL’s investment in ATC in 2015 and 2016, and the unallocated portions of the utility business. Refer to Note 6(a) for discussion of WPL’s transfer of its investment in ATC to ATI as of December 31, 2016. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2017 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,295.8 |  |  |  | $174.9 |  |  |  | $2.1 |  |  |  | $1,472.8 |
Depreciation and amortization | 196.9 |  |  | 16.0 |  |  | — |  |  | 212.9 |
Operating income (loss) | 305.4 |  |  | 24.5 |  |  | (6.7 | ) |  | 323.2 |
Interest expense |  |  |  |  |  |  | 93.8 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | )
Income taxes |  |  |  |  |  |  | 61.9 |
Earnings available for common stock |  |  |  |  |  |  | 186.6 |
Total assets | 4,871.8 |  |  | 471.9 |  |  | 412.8 |  |  | 5,756.5 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |
Construction and acquisition expenditures | 592.4 |  |  | 44.5 |  |  | 0.5 |  |  | 637.4 |
2016 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,305.8 |  |  |  | $151.4 |  |  |  | $1.9 |  |  |  | $1,459.1 |
Depreciation and amortization | 177.6 |  |  | 14.9 |  |  | — |  |  | 192.5 |
Operating income (loss) | 319.9 |  |  | 15.2 |  |  | (8.1 | ) |  | 327.0 |
Interest expense |  |  |  |  |  |  | 91.4 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | (39.1 | ) |  | (39.8 | )
Income taxes |  |  |  |  |  |  | 93.3 |
Earnings available for common stock |  |  |  |  |  |  | 190.4 |
Total assets | 4,444.7 |  |  | 437.8 |  |  | 407.8 |  |  | 5,290.3 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |
Construction and acquisition expenditures | 395.9 |  |  | 45.6 |  |  | 11.5 |  |  | 453.0 |
2015 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,266.7 |  |  |  | $163.9 |  |  |  | $4.5 |  |  |  | $1,435.1 |
Depreciation and amortization | 170.7 |  |  | 13.6 |  |  | — |  |  | 184.3 |
Operating income (loss) | 295.3 |  |  | 16.9 |  |  | (3.5 | ) |  | 308.7 |
Interest expense |  |  |  |  |  |  | 92.4 |
Equity income from unconsolidated investments | (0.9 | ) |  | — |  |  | (34.2 | ) |  | (35.1 | )
Income taxes |  |  |  |  |  |  | 82.9 |
Earnings available for common stock |  |  |  |  |  |  | 176.3 |
Total assets | 4,163.9 |  |  | 391.1 |  |  | 715.4 |  |  | 5,270.4 |
Investments in equity method subsidiaries | 8.7 |  |  | — |  |  | 293.3 |  |  | 302.0 |
Construction and acquisition expenditures | 291.3 |  |  | 49.7 |  |  | 3.3 |  |  | 344.3 |
IPL [Member] |
Segment Reporting Information [Line Items] |
Segments Of Business | SEGMENTS OF BUSINESS In the fourth quarter of 2017, Alliant Energy and WPL modified the segment reporting related to their ATC Investment, consistent with information used by their chief operating decision maker to evaluate performance and allocate resources. As of December 31, 2017, the ATC Investment is no longer included in Alliant Energy’s utility electric operations reportable segment or WPL’s electric operations reportable segment. As a result, all prior period amounts impacted by this change were reclassified to conform to the new presentation. Alliant Energy’s related amounts were reclassified from “Electric Utility” to “ATC Investment, Non-Utility, Parent and Other.” WPL’s related amounts were reclassified from “Electric” to “Other.” Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2017 are:
• | Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.”
• | ATC Investment, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s ATC Investment, Transportation, a non-utility wind investment, the Sheboygan Falls Energy Facility and other non-utility investments, which are described in Note 1(a).
Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2017 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,894.7 |  |  |  | $400.9 |  |  |  | $47.5 |  |  |  | $3,343.1 |  |  |  | $39.1 |  |  |  | $3,382.2 |
Depreciation and amortization | 412.0 |  |  | 38.2 |  |  | 7.7 |  |  | 457.9 |  |  | 3.9 |  |  | 461.8 |
Operating income (loss) | 586.5 |  |  | 45.3 |  |  | (11.7 | ) |  | 620.1 |  |  | 33.3 |  |  | 653.4 |
Interest expense |  |  |  |  |  |  | 206.2 |  |  | 9.4 |  |  | 215.6 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (44.1 | ) |  | (44.8 | )
Income taxes |  |  |  |  |  |  | 51.0 |  |  | 15.7 |  |  | 66.7 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 403.4 |  |  | 53.9 |  |  | 457.3 |
Total assets | 11,396.2 |  |  | 1,199.8 |  |  | 766.5 |  |  | 13,362.5 |  |  | 825.3 |  |  | 14,187.8 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |  |  | 373.1 |  |  | 381.4 |
Construction and acquisition expenditures | 1,154.9 |  |  | 125.2 |  |  | 1.7 |  |  | 1,281.8 |  |  | 185.1 |  |  | 1,466.9 |
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2016 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,875.5 |  |  |  | $355.4 |  |  |  | $48.6 |  |  |  | $3,279.5 |  |  |  | $40.5 |  |  |  | $3,320.0 |
Depreciation and amortization | 367.0 |  |  | 34.2 |  |  | 2.1 |  |  | 403.3 |  |  | 8.3 |  |  | 411.6 |
Operating income (loss) | 571.9 |  |  | 30.7 |  |  | (4.8 | ) |  | 597.8 |  |  | (60.8 | ) |  | 537.0 |
Interest expense |  |  |  |  |  |  | 194.6 |  |  | 1.6 |  |  | 196.2 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (38.9 | ) |  | (39.6 | )
Income tax expense (benefit) |  |  |  |  |  |  | 71.4 |  |  | (12.0 | ) |  | 59.4 |
Net income (loss) attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 385.2 |  |  | (13.7 | ) |  | 371.5 |
Total assets | 10,722.9 |  |  | 1,091.1 |  |  | 781.0 |  |  | 12,595.0 |  |  | 778.8 |  |  | 13,373.8 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |  |  | 318.3 |  |  | 326.0 |
Construction and acquisition expenditures | 994.0 |  |  | 137.1 |  |  | 0.1 |  |  | 1,131.2 |  |  | 65.6 |  |  | 1,196.8 |
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2015 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,770.5 |  |  |  | $381.2 |  |  |  | $57.9 |  |  |  | $3,209.6 |  |  |  | $44.0 |  |  |  | $3,253.6 |
Depreciation and amortization | 358.6 |  |  | 31.1 |  |  | 1.8 |  |  | 391.5 |  |  | 9.8 |  |  | 401.3 |
Operating income | 514.1 |  |  | 34.6 |  |  | 1.9 |  |  | 550.6 |  |  | 26.4 |  |  | 577.0 |
Interest expense |  |  |  |  |  |  | 189.2 |  |  | (2.1 | ) |  | 187.1 |
Equity income from unconsolidated investments, net | (0.9 | ) |  | — |  |  | — |  |  | (0.9 | ) |  | (32.9 | ) |  | (33.8 | )
Income taxes |  |  |  |  |  |  | 46.2 |  |  | 24.2 |  |  | 70.4 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 343.4 |  |  | 34.8 |  |  | 378.2 |
Total assets | 9,918.0 |  |  | 939.3 |  |  | 828.9 |  |  | 11,686.2 |  |  | 809.0 |  |  | 12,495.2 |
Investments in equity method subsidiaries | 8.7 |  |  | — |  |  | — |  |  | 8.7 |  |  | 294.2 |  |  | 302.9 |
Construction and acquisition expenditures | 852.5 |  |  | 106.4 |  |  | 1.4 |  |  | 960.3 |  |  | 74.0 |  |  | 1,034.3 |
IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2017 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,598.9 |  |  |  | $226.0 |  |  |  | $45.4 |  |  |  | $1,870.3 |
Depreciation and amortization | 215.1 |  |  | 22.2 |  |  | 7.7 |  |  | 245.0 |
Operating income (loss) | 281.1 |  |  | 20.8 |  |  | (5.0 | ) |  | 296.9 |
Interest expense |  |  |  |  |  |  | 112.4 |
Income tax benefit |  |  |  |  |  |  | (10.9 | )
Earnings available for common stock |  |  |  |  |  |  | 216.8 |
Total assets | 6,524.4 |  |  | 727.9 |  |  | 353.7 |  |  | 7,606.0 |
Construction and acquisition expenditures | 594.1 |  |  | 80.7 |  |  | 1.2 |  |  | 676.0 |
2016 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,569.7 |  |  |  | $204.0 |  |  |  | $46.7 |  |  |  | $1,820.4 |
Depreciation and amortization | 189.4 |  |  | 19.3 |  |  | 2.1 |  |  | 210.8 |
Operating income | 252.0 |  |  | 15.5 |  |  | 3.3 |  |  | 270.8 |
Interest expense |  |  |  |  |  |  | 103.2 |
Income tax benefit |  |  |  |  |  |  | (5.9 | )
Earnings available for common stock |  |  |  |  |  |  | 215.6 |
Total assets | 6,278.2 |  |  | 653.3 |  |  | 373.2 |  |  | 7,304.7 |
Construction and acquisition expenditures | 598.1 |  |  | 91.5 |  |  | 0.1 |  |  | 689.7 |
2015 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,503.8 |  |  |  | $217.3 |  |  |  | $53.4 |  |  |  | $1,774.5 |
Depreciation and amortization | 187.9 |  |  | 17.5 |  |  | 1.8 |  |  | 207.2 |
Operating income | 218.8 |  |  | 17.7 |  |  | 5.4 |  |  | 241.9 |
Interest expense |  |  |  |  |  |  | 96.8 |
Income tax benefit |  |  |  |  |  |  | (22.7 | )
Earnings available for common stock |  |  |  |  |  |  | 186.0 |
Total assets | 5,754.1 |  |  | 548.2 |  |  | 406.8 |  |  | 6,709.1 |
Construction and acquisition expenditures | 561.2 |  |  | 56.7 |  |  | 1.4 |  |  | 619.3 |
WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes WPL’s investment in ATC in 2015 and 2016, and the unallocated portions of the utility business. Refer to Note 6(a) for discussion of WPL’s transfer of its investment in ATC to ATI as of December 31, 2016. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2017 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,295.8 |  |  |  | $174.9 |  |  |  | $2.1 |  |  |  | $1,472.8 |
Depreciation and amortization | 196.9 |  |  | 16.0 |  |  | — |  |  | 212.9 |
Operating income (loss) | 305.4 |  |  | 24.5 |  |  | (6.7 | ) |  | 323.2 |
Interest expense |  |  |  |  |  |  | 93.8 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | )
Income taxes |  |  |  |  |  |  | 61.9 |
Earnings available for common stock |  |  |  |  |  |  | 186.6 |
Total assets | 4,871.8 |  |  | 471.9 |  |  | 412.8 |  |  | 5,756.5 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |
Construction and acquisition expenditures | 592.4 |  |  | 44.5 |  |  | 0.5 |  |  | 637.4 |
2016 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,305.8 |  |  |  | $151.4 |  |  |  | $1.9 |  |  |  | $1,459.1 |
Depreciation and amortization | 177.6 |  |  | 14.9 |  |  | — |  |  | 192.5 |
Operating income (loss) | 319.9 |  |  | 15.2 |  |  | (8.1 | ) |  | 327.0 |
Interest expense |  |  |  |  |  |  | 91.4 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | (39.1 | ) |  | (39.8 | )
Income taxes |  |  |  |  |  |  | 93.3 |
Earnings available for common stock |  |  |  |  |  |  | 190.4 |
Total assets | 4,444.7 |  |  | 437.8 |  |  | 407.8 |  |  | 5,290.3 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |
Construction and acquisition expenditures | 395.9 |  |  | 45.6 |  |  | 11.5 |  |  | 453.0 |
2015 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,266.7 |  |  |  | $163.9 |  |  |  | $4.5 |  |  |  | $1,435.1 |
Depreciation and amortization | 170.7 |  |  | 13.6 |  |  | — |  |  | 184.3 |
Operating income (loss) | 295.3 |  |  | 16.9 |  |  | (3.5 | ) |  | 308.7 |
Interest expense |  |  |  |  |  |  | 92.4 |
Equity income from unconsolidated investments | (0.9 | ) |  | — |  |  | (34.2 | ) |  | (35.1 | )
Income taxes |  |  |  |  |  |  | 82.9 |
Earnings available for common stock |  |  |  |  |  |  | 176.3 |
Total assets | 4,163.9 |  |  | 391.1 |  |  | 715.4 |  |  | 5,270.4 |
Investments in equity method subsidiaries | 8.7 |  |  | — |  |  | 293.3 |  |  | 302.0 |
Construction and acquisition expenditures | 291.3 |  |  | 49.7 |  |  | 3.3 |  |  | 344.3 |
WPL [Member] |
Segment Reporting Information [Line Items] |
Segments Of Business | SEGMENTS OF BUSINESS In the fourth quarter of 2017, Alliant Energy and WPL modified the segment reporting related to their ATC Investment, consistent with information used by their chief operating decision maker to evaluate performance and allocate resources. As of December 31, 2017, the ATC Investment is no longer included in Alliant Energy’s utility electric operations reportable segment or WPL’s electric operations reportable segment. As a result, all prior period amounts impacted by this change were reclassified to conform to the new presentation. Alliant Energy’s related amounts were reclassified from “Electric Utility” to “ATC Investment, Non-Utility, Parent and Other.” WPL’s related amounts were reclassified from “Electric” to “Other.” Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2017 are:
• | Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.”
• | ATC Investment, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s ATC Investment, Transportation, a non-utility wind investment, the Sheboygan Falls Energy Facility and other non-utility investments, which are described in Note 1(a).
Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2017 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,894.7 |  |  |  | $400.9 |  |  |  | $47.5 |  |  |  | $3,343.1 |  |  |  | $39.1 |  |  |  | $3,382.2 |
Depreciation and amortization | 412.0 |  |  | 38.2 |  |  | 7.7 |  |  | 457.9 |  |  | 3.9 |  |  | 461.8 |
Operating income (loss) | 586.5 |  |  | 45.3 |  |  | (11.7 | ) |  | 620.1 |  |  | 33.3 |  |  | 653.4 |
Interest expense |  |  |  |  |  |  | 206.2 |  |  | 9.4 |  |  | 215.6 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (44.1 | ) |  | (44.8 | )
Income taxes |  |  |  |  |  |  | 51.0 |  |  | 15.7 |  |  | 66.7 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 403.4 |  |  | 53.9 |  |  | 457.3 |
Total assets | 11,396.2 |  |  | 1,199.8 |  |  | 766.5 |  |  | 13,362.5 |  |  | 825.3 |  |  | 14,187.8 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |  |  | 373.1 |  |  | 381.4 |
Construction and acquisition expenditures | 1,154.9 |  |  | 125.2 |  |  | 1.7 |  |  | 1,281.8 |  |  | 185.1 |  |  | 1,466.9 |
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2016 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,875.5 |  |  |  | $355.4 |  |  |  | $48.6 |  |  |  | $3,279.5 |  |  |  | $40.5 |  |  |  | $3,320.0 |
Depreciation and amortization | 367.0 |  |  | 34.2 |  |  | 2.1 |  |  | 403.3 |  |  | 8.3 |  |  | 411.6 |
Operating income (loss) | 571.9 |  |  | 30.7 |  |  | (4.8 | ) |  | 597.8 |  |  | (60.8 | ) |  | 537.0 |
Interest expense |  |  |  |  |  |  | 194.6 |  |  | 1.6 |  |  | 196.2 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (38.9 | ) |  | (39.6 | )
Income tax expense (benefit) |  |  |  |  |  |  | 71.4 |  |  | (12.0 | ) |  | 59.4 |
Net income (loss) attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 385.2 |  |  | (13.7 | ) |  | 371.5 |
Total assets | 10,722.9 |  |  | 1,091.1 |  |  | 781.0 |  |  | 12,595.0 |  |  | 778.8 |  |  | 13,373.8 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |  |  | 318.3 |  |  | 326.0 |
Construction and acquisition expenditures | 994.0 |  |  | 137.1 |  |  | 0.1 |  |  | 1,131.2 |  |  | 65.6 |  |  | 1,196.8 |
|  |  |  |  |  |  |  |  | ATC Investment, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2015 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Operating revenues |  | $2,770.5 |  |  |  | $381.2 |  |  |  | $57.9 |  |  |  | $3,209.6 |  |  |  | $44.0 |  |  |  | $3,253.6 |
Depreciation and amortization | 358.6 |  |  | 31.1 |  |  | 1.8 |  |  | 391.5 |  |  | 9.8 |  |  | 401.3 |
Operating income | 514.1 |  |  | 34.6 |  |  | 1.9 |  |  | 550.6 |  |  | 26.4 |  |  | 577.0 |
Interest expense |  |  |  |  |  |  | 189.2 |  |  | (2.1 | ) |  | 187.1 |
Equity income from unconsolidated investments, net | (0.9 | ) |  | — |  |  | — |  |  | (0.9 | ) |  | (32.9 | ) |  | (33.8 | )
Income taxes |  |  |  |  |  |  | 46.2 |  |  | 24.2 |  |  | 70.4 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 343.4 |  |  | 34.8 |  |  | 378.2 |
Total assets | 9,918.0 |  |  | 939.3 |  |  | 828.9 |  |  | 11,686.2 |  |  | 809.0 |  |  | 12,495.2 |
Investments in equity method subsidiaries | 8.7 |  |  | — |  |  | — |  |  | 8.7 |  |  | 294.2 |  |  | 302.9 |
Construction and acquisition expenditures | 852.5 |  |  | 106.4 |  |  | 1.4 |  |  | 960.3 |  |  | 74.0 |  |  | 1,034.3 |
IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2017 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,598.9 |  |  |  | $226.0 |  |  |  | $45.4 |  |  |  | $1,870.3 |
Depreciation and amortization | 215.1 |  |  | 22.2 |  |  | 7.7 |  |  | 245.0 |
Operating income (loss) | 281.1 |  |  | 20.8 |  |  | (5.0 | ) |  | 296.9 |
Interest expense |  |  |  |  |  |  | 112.4 |
Income tax benefit |  |  |  |  |  |  | (10.9 | )
Earnings available for common stock |  |  |  |  |  |  | 216.8 |
Total assets | 6,524.4 |  |  | 727.9 |  |  | 353.7 |  |  | 7,606.0 |
Construction and acquisition expenditures | 594.1 |  |  | 80.7 |  |  | 1.2 |  |  | 676.0 |
2016 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,569.7 |  |  |  | $204.0 |  |  |  | $46.7 |  |  |  | $1,820.4 |
Depreciation and amortization | 189.4 |  |  | 19.3 |  |  | 2.1 |  |  | 210.8 |
Operating income | 252.0 |  |  | 15.5 |  |  | 3.3 |  |  | 270.8 |
Interest expense |  |  |  |  |  |  | 103.2 |
Income tax benefit |  |  |  |  |  |  | (5.9 | )
Earnings available for common stock |  |  |  |  |  |  | 215.6 |
Total assets | 6,278.2 |  |  | 653.3 |  |  | 373.2 |  |  | 7,304.7 |
Construction and acquisition expenditures | 598.1 |  |  | 91.5 |  |  | 0.1 |  |  | 689.7 |
2015 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,503.8 |  |  |  | $217.3 |  |  |  | $53.4 |  |  |  | $1,774.5 |
Depreciation and amortization | 187.9 |  |  | 17.5 |  |  | 1.8 |  |  | 207.2 |
Operating income | 218.8 |  |  | 17.7 |  |  | 5.4 |  |  | 241.9 |
Interest expense |  |  |  |  |  |  | 96.8 |
Income tax benefit |  |  |  |  |  |  | (22.7 | )
Earnings available for common stock |  |  |  |  |  |  | 186.0 |
Total assets | 5,754.1 |  |  | 548.2 |  |  | 406.8 |  |  | 6,709.1 |
Construction and acquisition expenditures | 561.2 |  |  | 56.7 |  |  | 1.4 |  |  | 619.3 |
WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes WPL’s investment in ATC in 2015 and 2016, and the unallocated portions of the utility business. Refer to Note 6(a) for discussion of WPL’s transfer of its investment in ATC to ATI as of December 31, 2016. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2017 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,295.8 |  |  |  | $174.9 |  |  |  | $2.1 |  |  |  | $1,472.8 |
Depreciation and amortization | 196.9 |  |  | 16.0 |  |  | — |  |  | 212.9 |
Operating income (loss) | 305.4 |  |  | 24.5 |  |  | (6.7 | ) |  | 323.2 |
Interest expense |  |  |  |  |  |  | 93.8 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | )
Income taxes |  |  |  |  |  |  | 61.9 |
Earnings available for common stock |  |  |  |  |  |  | 186.6 |
Total assets | 4,871.8 |  |  | 471.9 |  |  | 412.8 |  |  | 5,756.5 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |
Construction and acquisition expenditures | 592.4 |  |  | 44.5 |  |  | 0.5 |  |  | 637.4 |
2016 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,305.8 |  |  |  | $151.4 |  |  |  | $1.9 |  |  |  | $1,459.1 |
Depreciation and amortization | 177.6 |  |  | 14.9 |  |  | — |  |  | 192.5 |
Operating income (loss) | 319.9 |  |  | 15.2 |  |  | (8.1 | ) |  | 327.0 |
Interest expense |  |  |  |  |  |  | 91.4 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | (39.1 | ) |  | (39.8 | )
Income taxes |  |  |  |  |  |  | 93.3 |
Earnings available for common stock |  |  |  |  |  |  | 190.4 |
Total assets | 4,444.7 |  |  | 437.8 |  |  | 407.8 |  |  | 5,290.3 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |
Construction and acquisition expenditures | 395.9 |  |  | 45.6 |  |  | 11.5 |  |  | 453.0 |
2015 | Electric |  | Gas |  | Other |  | Total
Operating revenues |  | $1,266.7 |  |  |  | $163.9 |  |  |  | $4.5 |  |  |  | $1,435.1 |
Depreciation and amortization | 170.7 |  |  | 13.6 |  |  | — |  |  | 184.3 |
Operating income (loss) | 295.3 |  |  | 16.9 |  |  | (3.5 | ) |  | 308.7 |
Interest expense |  |  |  |  |  |  | 92.4 |
Equity income from unconsolidated investments | (0.9 | ) |  | — |  |  | (34.2 | ) |  | (35.1 | )
Income taxes |  |  |  |  |  |  | 82.9 |
Earnings available for common stock |  |  |  |  |  |  | 176.3 |
Total assets | 4,163.9 |  |  | 391.1 |  |  | 715.4 |  |  | 5,270.4 |
Investments in equity method subsidiaries | 8.7 |  |  | — |  |  | 293.3 |  |  | 302.0 |
Construction and acquisition expenditures | 291.3 |  |  | 49.7 |  |  | 3.3 |  |  | 344.3 |

X
- Definition The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9038-108599 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8971-108599 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8595-108599 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8380-108599 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8933-108599 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8844-108599 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 35 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8984-108599 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9031-108599 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9054-108599 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8538-108599 Reference 12: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 29 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8864-108599 Reference 13: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 31 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8924-108599 Reference 14: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8906-108599 + Details
Name: | us-gaap_SegmentReportingDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
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: |