Alliant Energy (LNT) 10-Q 2 Aug 19 2019 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	6 Months Ended
	Jun. 30, 2019shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity Registrant Name	ALLIANT ENERGY CORP
Entity Central Index Key	0000352541
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	1-9894
Entity Tax Identification Number	39-1380265
Title of 12(b) Security	Common Stock, $0.01 Par Value
Trading Symbol	LNT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	237,521,074
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
IPL [Member]
Entity Information [Line Items]
Entity Registrant Name	INTERSTATE POWER & LIGHT CO
Entity Central Index Key	0000052485
Entity Incorporation, State or Country Code	IA
Entity Address, Address Line One	Alliant Energy Tower
Entity Address, City or Town	Cedar Rapids
Entity Address, State or Province	IA
Entity Address, Postal Zip Code	52401
City Area Code	319
Local Phone Number	786-4411
Entity File Number	1-4117
Entity Tax Identification Number	42-0331370
Title of 12(b) Security	5.100% Series D Cumulative Perpetual Preferred Stock, $0.01 Par Value
Trading Symbol	IPLDP
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	13,370,788
WPL [Member]
Entity Information [Line Items]
Entity Registrant Name	WISCONSIN POWER & LIGHT CO
Entity Central Index Key	0000107832
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	0-337
Entity Tax Identification Number	39-0714890
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	13,236,601

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Electric utility	$ 691.2	$ 726.3	$ 1,434.6	$ 1,435
Gas utility	65.2	68.6	281	254.2
Other utility	10.9	10.7	22	23.9
Non-utility	22.9	10.5	39.8	19.3
Total revenues	790.2	816.1	1,777.4	1,732.4
Operating expenses:
Electric production fuel and purchased power	164.8	208.5	383.2	411.7
Electric transmission service	112.4	119.7	235.4	246.1
Cost of gas sold	20.4	27.5	142	138.7
Other operation and maintenance	172.3	158	353.5	320.4
Depreciation and amortization	142.9	127	279.8	247.4
Taxes other than income taxes	27.6	24.2	56.9	51.2
Total operating expenses	640.4	664.9	1,450.8	1,415.5
Operating income	149.8	151.2	326.6	316.9
Other (income) and deductions:
Interest expense	69.2	61.3	135.5	120.5
Equity income from unconsolidated investments, net	(12.7)	(10.5)	(23.6)	(31.8)
Allowance for funds used during construction	(18.3)	(18.1)	(43.7)	(33)
Other	3.3	2	7.3	4.4
Total other (income) and deductions	41.5	34.7	75.5	60.1
Income before income taxes	108.3	116.5	251.1	256.8
Income taxes	11.2	13.6	26.3	30.4
Net income	97.1	102.9	224.8	226.4
Preferred dividend requirements of Interstate Power and Light Company	2.5	2.5	5.1	5.1
Net income attributable to common shareowners	$ 94.6	$ 100.4	$ 219.7	$ 221.3
Weighted average number of common shares outstanding (basic) (in shares)	237.5	232	237	231.7
Weighted average number of common shares outstanding (diluted) (in shares)	238.1	232	237.3	231.7
Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic and diluted) (in dollars per share)	$ 0.40	$ 0.43	$ 0.93	$ 0.96
IPL [Member]
Revenues:
Electric utility	$ 392.3	$ 422.1	$ 812.1	$ 827.8
Gas utility	38.4	42.2	163	150.3
Other utility	10.5	10.5	21.2	22.5
Total revenues	441.2	474.8	996.3	1,000.6
Operating expenses:
Electric production fuel and purchased power	83.3	116.9	212.2	231.5
Electric transmission service	77.4	84.4	165.1	175.2
Cost of gas sold	10.8	16.8	74.1	77.4
Other operation and maintenance	97.4	97	205.4	202.5
Depreciation and amortization	82.6	70.5	159.7	135.3
Taxes other than income taxes	15.2	11.5	31.8	25.4
Total operating expenses	366.7	397.1	848.3	847.3
Operating income	74.5	77.7	148	153.3
Other (income) and deductions:
Interest expense	31.5	30.4	60.9	60.2
Allowance for funds used during construction	(7.9)	(9.9)	(23.7)	(17.3)
Other	1.5	0.7	3.4	1.5
Total other (income) and deductions	25.1	21.2	40.6	44.4
Income before income taxes	49.4	56.5	107.4	108.9
Income taxes	1.9	2.3	4	5.4
Net income	47.5	54.2	103.4	103.5
Preferred dividend requirements of Interstate Power and Light Company	2.5	2.5	5.1	5.1
Net income attributable to common shareowners	45	51.7	98.3	98.4
WPL [Member]
Revenues:
Electric utility	298.9	304.2	622.5	607.2
Gas utility	26.8	26.4	118	103.9
Other utility	0.4	0.2	0.8	1.4
Total revenues	326.1	330.8	741.3	712.5
Operating expenses:
Electric production fuel and purchased power	81.5	91.6	171	180.2
Electric transmission service	35	35.3	70.3	70.9
Cost of gas sold	9.6	10.7	67.9	61.3
Other operation and maintenance	62.4	62.3	125.9	118.6
Depreciation and amortization	59.1	55.5	117.7	110.1
Taxes other than income taxes	11.5	12	23.4	24
Total operating expenses	259.1	267.4	576.2	565.1
Operating income	67	63.4	165.1	147.4
Other (income) and deductions:
Interest expense	26.1	24.6	51.9	49.3
Allowance for funds used during construction	(10.4)	(8.2)	(20)	(15.7)
Other	1.6	1	3.2	2.1
Total other (income) and deductions	17.3	17.4	35.1	35.7
Income before income taxes	49.7	46	130	111.7
Income taxes	7.7	6.2	22.3	17.9
Net income			107.7	93.8
Net income attributable to common shareowners	$ 42	$ 39.8	$ 107.7	$ 93.8

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 170.2	$ 20.9
Accounts receivable, less allowance for doubtful accounts	421.5	350.4
Production fuel, at weighted average cost	67.8	61.4
Gas stored underground, at weighted average cost	32.9	49
Materials and supplies, at weighted average cost	105.1	101.4
Regulatory assets	78.7	79.8
Other	151.1	122.2
Total current assets	1,027.3	785.1
Property, plant and equipment, net	12,854	12,462.4
Investments:
ATC Holdings	302.3	293.6
Other	141	137.7
Total investments	443.3	431.3
Other assets:
Regulatory assets	1,728.2	1,657.5
Deferred charges and other	68.8	89.7
Total other assets	1,797	1,747.2
Total assets	16,121.6	15,426
Current liabilities:
Current maturities of long-term debt	706.8	256.5
Commercial paper	390.5	441.2
Accounts payable	422.5	543.3
Regulatory liabilities	166.9	142.7
Other	262.3	260.4
Total current liabilities	1,949	1,644.1
Long-term debt, net (excluding current portion)	5,438.1	5,246.3
Other liabilities:
Deferred tax liabilities	1,657.9	1,603.1
Regulatory liabilities	1,276	1,350.5
Pension and other benefit obligations	487.4	509.1
Other	413.6	287.2
Total other liabilities	3,834.9	3,749.9
Commitments and contingencies (Note 14)
Common equity:
Common stock	2.4	2.4
Additional paid-in capital	2,108.4	2,045.5
Retained earnings	2,597.8	2,545.9
Accumulated other comprehensive income	1	1.7
Shares in deferred compensation trust - 380,863 and 384,580 shares at a weighted average cost of $26.22 and $25.60 per share	(10)	(9.8)
Total common equity	4,699.6	4,585.7
Cumulative preferred stock of Interstate Power and Light Company	200	200
Total equity	4,899.6	4,785.7
Total liabilities and equity	16,121.6	15,426
IPL [Member]
Current assets:
Cash and cash equivalents	5	9.7
Accounts receivable, less allowance for doubtful accounts	231.7	153.5
Production fuel, at weighted average cost	37.8	44.8
Gas stored underground, at weighted average cost	11.8	26.1
Materials and supplies, at weighted average cost	58	55.4
Regulatory assets	33.8	39.2
Other	21.7	43.1
Total current assets	399.8	371.8
Property, plant and equipment, net	7,080.4	6,781.5
Other assets:
Regulatory assets	1,330.7	1,239.8
Deferred charges and other	19.6	18.3
Total other assets	1,350.3	1,258.1
Total assets	8,830.5	8,411.4
Current liabilities:
Commercial paper	0	50.4
Accounts payable	216.8	304.9
Accounts payable to associated companies	43	28.8
Regulatory liabilities	82.1	90
Accrued taxes	64.7	45.8
Other	87.8	87.2
Total current liabilities	494.4	607.1
Long-term debt, net (excluding current portion)	2,850.5	2,552.3
Other liabilities:
Deferred tax liabilities	971.2	957.3
Regulatory liabilities	637.8	664.9
Pension and other benefit obligations	171	178.4
Other	360.5	220.7
Total other liabilities	2,140.5	2,021.3
Commitments and contingencies (Note 14)
Common equity:
Common stock	33.4	33.4
Additional paid-in capital	2,322.8	2,222.8
Retained earnings	788.9	774.5
Total common equity	3,145.1	3,030.7
Cumulative preferred stock of Interstate Power and Light Company	200	200
Total equity	3,345.1	3,230.7
Total liabilities and equity	8,830.5	8,411.4
WPL [Member]
Current assets:
Cash and cash equivalents	163.2	8.7
Accounts receivable, less allowance for doubtful accounts	180.9	190.1
Production fuel, at weighted average cost	30	16.6
Gas stored underground, at weighted average cost	21.1	22.9
Materials and supplies, at weighted average cost	44.3	42.9
Regulatory assets	44.9	40.6
Other	108.8	62.8
Total current assets	593.2	384.6
Property, plant and equipment, net	5,377.5	5,287.3
Other assets:
Regulatory assets	397.5	417.7
Deferred charges and other	21.8	62.9
Total other assets	419.3	480.6
Total assets	6,390	6,152.5
Current liabilities:
Current maturities of long-term debt	400	250
Commercial paper	0	105.5
Accounts payable	150	180.9
Regulatory liabilities	84.8	52.7
Other	109.1	105.5
Total current liabilities	743.9	694.6
Long-term debt, net (excluding current portion)	1,781.8	1,584.9
Other liabilities:
Deferred tax liabilities	615.1	582
Regulatory liabilities	638.2	685.6
Finance lease obligations - Sheboygan Falls Energy Facility	55.8	60
Pension and other benefit obligations	210.5	217.7
Other	159.5	178.2
Total other liabilities	1,679.1	1,723.5
Commitments and contingencies (Note 14)
Common equity:
Common stock	66.2	66.2
Additional paid-in capital	1,309	1,309
Retained earnings	810	774.3
Total common equity	2,185.2	2,149.5
Total equity	2,185.2	2,149.5
Total liabilities and equity	$ 6,390	$ 6,152.5

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	237,521,074	236,063,279
Shares in deferred compensation trust (in shares)	380,863	384,580
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 26.22	$ 25.60
IPL [Member]
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	24,000,000	24,000,000
Common stock, shares outstanding (in shares)	13,370,788	13,370,788
WPL [Member]
Common stock, par value	$ 5	$ 5
Common stock, shares authorized (in shares)	18,000,000	18,000,000
Common stock, shares outstanding (in shares)	13,236,601	13,236,601

Condensed Consolidated Statem_2

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 224.8	$ 226.4
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	279.8	247.4
Deferred tax expense (benefit) and tax credits	19.9	33.9
Equity component of allowance for funds used during construction	(30.8)	(22.6)
Equity income from unconsolidated investments, net	(23.6)	(31.8)
Other	37.1	31.6
Other changes in assets and liabilities:
Accounts receivable	(199.7)	(168.4)
Accounts payable	(33.1)	(34.1)
Regulatory liabilities	(26.1)	21.5
Deferred income taxes	34.3	(6.3)
Other	(5.7)	(23.2)
Net cash flows from operating activities	276.9	274.4
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(652.5)	(699.6)
Other construction and acquisition expenditures	(54.1)	(33.7)
Cash receipts on sold receivables	125.5	232.5
Other	(25.9)	(17.1)
Net cash flows used for investing activities	(607)	(517.9)
Cash flows from financing activities:
Common stock dividends	(167.8)	(154.8)
Proceeds from issuance of common stock, net	60.6	100.1
Proceeds from issuance of long-term debt	650	1,000
Payments to retire long-term debt	(3.4)	(503)
Net change in commercial paper and other short-term borrowings	(50.7)	(207.7)
Other	(9.9)	(13)
Net cash flows from financing activities	478.8	221.6
Net increase (decrease) in cash, cash equivalents and restricted cash	148.7	(21.9)
Cash, cash equivalents and restricted cash at beginning of period	25.5	33.9
Cash, cash equivalents and restricted cash at end of period	174.2	12
Supplemental cash flows information:
Interest	(132.7)	(119.8)
Income taxes, net	2.5	(5)
Significant non-cash investing and financing activities:
Accrued capital expenditures	187.4	186.5
Beneficial interest obtained in exchange for securitized accounts receivable	214.6	208.3
IPL [Member]
Cash flows from operating activities:
Net income	103.4	103.5
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	159.7	135.3
Deferred tax expense (benefit) and tax credits	(11.7)	9.6
Other	(14.9)	(10.3)
Other changes in assets and liabilities:
Accounts receivable	(209.3)	(206.2)
Accounts payable	(17)	(29.3)
Accrued taxes	18.9	(2.1)
Deferred income taxes	25.3	(17.8)
Other	34.6	30.1
Net cash flows from operating activities	89	12.8
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(449.5)	(391.1)
Cash receipts on sold receivables	125.5	232.5
Other	(30.5)	(20.5)
Net cash flows used for investing activities	(354.5)	(179.1)
Cash flows from financing activities:
Common stock dividends	(83.9)	(84)
Capital contributions from parent	100	130
Proceeds from issuance of long-term debt	300	0
Net change in commercial paper and other short-term borrowings	(50.4)	125
Other	(6.2)	(6.6)
Net cash flows from financing activities	259.5	164.4
Net increase (decrease) in cash, cash equivalents and restricted cash	(6)	(1.9)
Cash, cash equivalents and restricted cash at beginning of period	12.4	7.2
Cash, cash equivalents and restricted cash at end of period	6.4	5.3
Supplemental cash flows information:
Interest	(58.3)	(60.2)
Income taxes, net	12.1	(0.5)
Significant non-cash investing and financing activities:
Accrued capital expenditures	117.4	93.4
Beneficial interest obtained in exchange for securitized accounts receivable	214.6	208.3
WPL [Member]
Cash flows from operating activities:
Net income	107.7	93.8
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	117.7	110.1
Deferred tax expense (benefit) and tax credits	21.7	14.5
Other	(4.7)	(8.1)
Other changes in assets and liabilities:
Accounts receivable	7.6	39
Accounts payable	(19.6)	(10.4)
Regulatory liabilities	(18.4)	2.5
Other	(3.8)	(15.5)
Net cash flows from operating activities	208.2	225.9
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(203)	(308.5)
Other	(15)	(17)
Net cash flows used for investing activities	(218)	(325.5)
Cash flows from financing activities:
Common stock dividends	(72)	(70.1)
Capital contributions from parent	0	150
Proceeds from issuance of long-term debt	350	0
Net change in commercial paper and other short-term borrowings	(105.5)	1.4
Other	(7.4)	(1.3)
Net cash flows from financing activities	165.1	80
Net increase (decrease) in cash, cash equivalents and restricted cash	155.3	(19.6)
Cash, cash equivalents and restricted cash at beginning of period	9.2	24.2
Cash, cash equivalents and restricted cash at end of period	164.5	4.6
Supplemental cash flows information:
Interest	(51.7)	(49.4)
Income taxes, net	(6.5)	(7.9)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 66.4	$ 89.6

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
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, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019 . 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 cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d) . NOTE 1(b) Cash and Cash Equivalents - At June 30, 2019 , Alliant Energy’s and WPL’s cash and cash equivalents included $161.8 million and $160.4 million of money market fund investments, with interest rates of 2.4% and 2.4% , respectively. NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term. NOTE 1(d) New Accounting Standards - Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial statements. Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements. 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. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. 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. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases. Cash Flows Statements - On January 1, 2018, Alliant Energy and IPL adopted an accounting standard that 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 and IPL currently use a method of presentation that allocates cash flows between operating and investing activities based on daily transactional activity. For the six months ended June 30, 2018 , Alliant Energy and IPL initially utilized a method of presentation that allocated cash flows between operating and investing activities based on monthly transactional activity. For the six months ended June 30, 2018 , the change in method of presentation to daily transactional activity increased Alliant Energy’s and IPL’s operating cash flows by $339.4 million , and Alliant Energy’s and IPL’s operating cash flows increased to $274.4 million and $12.8 million , respectively.
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, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019 . 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 cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d) . NOTE 1(b) Cash and Cash Equivalents - At June 30, 2019 , Alliant Energy’s and WPL’s cash and cash equivalents included $161.8 million and $160.4 million of money market fund investments, with interest rates of 2.4% and 2.4% , respectively. NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term. NOTE 1(d) New Accounting Standards - Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial statements. Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements. 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. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. 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. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases. Cash Flows Statements - On January 1, 2018, Alliant Energy and IPL adopted an accounting standard that 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 and IPL currently use a method of presentation that allocates cash flows between operating and investing activities based on daily transactional activity. For the six months ended June 30, 2018 , Alliant Energy and IPL initially utilized a method of presentation that allocated cash flows between operating and investing activities based on monthly transactional activity. For the six months ended June 30, 2018 , the change in method of presentation to daily transactional activity increased Alliant Energy’s and IPL’s operating cash flows by $339.4 million , and Alliant Energy’s and IPL’s operating cash flows increased to $274.4 million and $12.8 million , respectively.
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, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019 . 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 cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d) . NOTE 1(b) Cash and Cash Equivalents - At June 30, 2019 , Alliant Energy’s and WPL’s cash and cash equivalents included $161.8 million and $160.4 million of money market fund investments, with interest rates of 2.4% and 2.4% , respectively. NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term. NOTE 1(d) New Accounting Standards - Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial statements. Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements. 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. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. 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. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases. Cash Flows Statements - On January 1, 2018, Alliant Energy and IPL adopted an accounting standard that 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 and IPL currently use a method of presentation that allocates cash flows between operating and investing activities based on daily transactional activity. For the six months ended June 30, 2018 , Alliant Energy and IPL initially utilized a method of presentation that allocated cash flows between operating and investing activities based on monthly transactional activity. For the six months ended June 30, 2018 , the change in method of presentation to daily transactional activity increased Alliant Energy’s and IPL’s operating cash flows by $339.4 million , and Alliant Energy’s and IPL’s operating cash flows increased to $274.4 million and $12.8 million , respectively.

Regulatory Matters

Regulatory Matters	6 Months Ended
	Jun. 30, 2019
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $815.5 $820.6 $780.2 $783.1 $35.3 $37.5 Pension and OPEB costs 522.9 542.3 264.7 274.0 258.2 268.3 Asset retirement obligations 111.0 110.8 76.2 76.3 34.8 34.5 IPL’s DAEC PPA amendment 107.1 — 107.1 — — — EGUs retired early 102.8 111.6 51.7 55.4 51.1 56.2 Derivatives 30.6 28.0 13.4 15.1 17.2 12.9 Emission allowances 22.4 23.6 22.4 23.6 — — Other 94.6 100.4 48.8 51.5 45.8 48.9 $1,806.9 $1,737.3 $1,364.5 $1,279.0 $442.4 $458.3 Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $853.8 $890.6 $365.6 $390.1 $488.2 $500.5 Cost of removal obligations 399.2 401.2 269.5 273.3 129.7 127.9 Electric transmission cost recovery 101.5 104.0 52.7 47.7 48.8 56.3 WPL’s earnings sharing mechanism 25.2 25.4 — — 25.2 25.4 Commodity cost recovery 22.7 16.8 11.9 11.9 10.8 4.9 Other 40.5 55.2 20.2 31.9 20.3 23.3 $1,442.9 $1,493.2 $719.9 $754.9 $723.0 $738.3 IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by 5 years. The IUB approved placing the buyout payment in a regulatory asset account, which will be recovered from IPL’s retail customers over a 5 -year period following the payment. The offsetting obligation has been discounted and is recorded in “Other liabilities” on Alliant Energy’s and IPL’s balance sheets. Utility Rate Reviews IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers by $204 million , based on a 2020 forward-looking Test Period. The requested increase would take place in two phases, $90 million through interim rates and the remaining $114 million through final rates. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL currently expects the proposed retail electric base rate increase to be partially offset by cost reductions in non-base rate factors, including fuel-related and energy efficiency costs. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million , on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision. Intervenor testimony was filed in August 2019 addressing, among other things, the return on common equity percentage used to calculate the interim rate increase implemented in April 2019. Intervenors have also filed testimony addressing various positions on rate design and revenue requirement, including authorized returns on production tax credits carryforwards, for final rates. The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision from the IUB in the fourth quarter of 2019 on the interim rate increase, as well as the remaining $114 million of final rates, which would be effective in the first quarter of 2020. IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers by $21 million , based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects. IPL currently expects the proposed retail gas base rate increase to be partially offset by cost reductions in non-base rate factors, including lower cost of gas sold and energy efficiency costs. IPL currently expects a decision from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.
IPL [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $815.5 $820.6 $780.2 $783.1 $35.3 $37.5 Pension and OPEB costs 522.9 542.3 264.7 274.0 258.2 268.3 Asset retirement obligations 111.0 110.8 76.2 76.3 34.8 34.5 IPL’s DAEC PPA amendment 107.1 — 107.1 — — — EGUs retired early 102.8 111.6 51.7 55.4 51.1 56.2 Derivatives 30.6 28.0 13.4 15.1 17.2 12.9 Emission allowances 22.4 23.6 22.4 23.6 — — Other 94.6 100.4 48.8 51.5 45.8 48.9 $1,806.9 $1,737.3 $1,364.5 $1,279.0 $442.4 $458.3 Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $853.8 $890.6 $365.6 $390.1 $488.2 $500.5 Cost of removal obligations 399.2 401.2 269.5 273.3 129.7 127.9 Electric transmission cost recovery 101.5 104.0 52.7 47.7 48.8 56.3 WPL’s earnings sharing mechanism 25.2 25.4 — — 25.2 25.4 Commodity cost recovery 22.7 16.8 11.9 11.9 10.8 4.9 Other 40.5 55.2 20.2 31.9 20.3 23.3 $1,442.9 $1,493.2 $719.9 $754.9 $723.0 $738.3 IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by 5 years. The IUB approved placing the buyout payment in a regulatory asset account, which will be recovered from IPL’s retail customers over a 5 -year period following the payment. The offsetting obligation has been discounted and is recorded in “Other liabilities” on Alliant Energy’s and IPL’s balance sheets. Utility Rate Reviews IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers by $204 million , based on a 2020 forward-looking Test Period. The requested increase would take place in two phases, $90 million through interim rates and the remaining $114 million through final rates. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL currently expects the proposed retail electric base rate increase to be partially offset by cost reductions in non-base rate factors, including fuel-related and energy efficiency costs. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million , on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision. Intervenor testimony was filed in August 2019 addressing, among other things, the return on common equity percentage used to calculate the interim rate increase implemented in April 2019. Intervenors have also filed testimony addressing various positions on rate design and revenue requirement, including authorized returns on production tax credits carryforwards, for final rates. The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision from the IUB in the fourth quarter of 2019 on the interim rate increase, as well as the remaining $114 million of final rates, which would be effective in the first quarter of 2020. IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers by $21 million , based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects. IPL currently expects the proposed retail gas base rate increase to be partially offset by cost reductions in non-base rate factors, including lower cost of gas sold and energy efficiency costs. IPL currently expects a decision from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.
WPL [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $815.5 $820.6 $780.2 $783.1 $35.3 $37.5 Pension and OPEB costs 522.9 542.3 264.7 274.0 258.2 268.3 Asset retirement obligations 111.0 110.8 76.2 76.3 34.8 34.5 IPL’s DAEC PPA amendment 107.1 — 107.1 — — — EGUs retired early 102.8 111.6 51.7 55.4 51.1 56.2 Derivatives 30.6 28.0 13.4 15.1 17.2 12.9 Emission allowances 22.4 23.6 22.4 23.6 — — Other 94.6 100.4 48.8 51.5 45.8 48.9 $1,806.9 $1,737.3 $1,364.5 $1,279.0 $442.4 $458.3 Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $853.8 $890.6 $365.6 $390.1 $488.2 $500.5 Cost of removal obligations 399.2 401.2 269.5 273.3 129.7 127.9 Electric transmission cost recovery 101.5 104.0 52.7 47.7 48.8 56.3 WPL’s earnings sharing mechanism 25.2 25.4 — — 25.2 25.4 Commodity cost recovery 22.7 16.8 11.9 11.9 10.8 4.9 Other 40.5 55.2 20.2 31.9 20.3 23.3 $1,442.9 $1,493.2 $719.9 $754.9 $723.0 $738.3

Receivables

Receivables	6 Months Ended
	Jun. 30, 2019
Receivables [Line Items]
Receivables	RECEIVABLES Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of June 30, 2019 , IPL had $83 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Maximum outstanding aggregate cash proceeds $25.0 $116.0 $108.0 $116.0 Average outstanding aggregate cash proceeds 2.6 52.3 41.6 56.7 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2019 December 31, 2018 Customer accounts receivable $138.3 $140.1 Unbilled utility revenues 90.5 97.1 Other receivables 0.4 0.1 Receivables sold to third party 229.2 237.3 Less: cash proceeds 5.0 108.0 Deferred proceeds 224.2 129.3 Less: allowance for doubtful accounts 9.6 9.9 Fair value of deferred proceeds $214.6 $119.4 As of June 30, 2019 , outstanding receivables past due under the Receivables Agreement were $27.1 million . Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Collections $487.7 $483.7 $1,043.5 $1,000.7 Write-offs, net of recoveries 2.6 1.9 8.1 8.0
IPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of June 30, 2019 , IPL had $83 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Maximum outstanding aggregate cash proceeds $25.0 $116.0 $108.0 $116.0 Average outstanding aggregate cash proceeds 2.6 52.3 41.6 56.7 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2019 December 31, 2018 Customer accounts receivable $138.3 $140.1 Unbilled utility revenues 90.5 97.1 Other receivables 0.4 0.1 Receivables sold to third party 229.2 237.3 Less: cash proceeds 5.0 108.0 Deferred proceeds 224.2 129.3 Less: allowance for doubtful accounts 9.6 9.9 Fair value of deferred proceeds $214.6 $119.4 As of June 30, 2019 , outstanding receivables past due under the Receivables Agreement were $27.1 million . Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Collections $487.7 $483.7 $1,043.5 $1,000.7 Write-offs, net of recoveries 2.6 1.9 8.1 8.0

Investments and Acquisitions

Investments and Acquisitions	6 Months Ended
	Jun. 30, 2019
Schedule of Investments [Line Items]
Investments and Acquisitions	INVESTMENTS AND ACQUISITIONS Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and six months ended June 30 was as follows (in millions): Three Months Six Months 2019 2018 2019 2018 ATC Holdings ($10.0 ) ($7.8 ) ($19.5 ) ($16.5 ) Non-utility wind farm in Oklahoma (1.3 ) (2.5 ) (2.4 ) (14.6 ) Other (1.4 ) (0.2 ) (1.7 ) (0.7 ) ($12.7 ) ($10.5 ) ($23.6 ) ($31.8 ) Non-utility Transportation Acquisitions - In the first quarter of 2019, Alliant Energy, through its wholly-owned non-utility subsidiaries, completed acquisitions of freight management companies located in Cedar Rapids, Iowa and Stoughton, Wisconsin. These acquisitions were purchased for $21 million , including contingent consideration of $8 million , which is expected to be paid within two years . The purchase price was largely allocated to intangibles and the remainder was allocated to working capital and property.

Common Equity

Common Equity	6 Months Ended
	Jun. 30, 2019
Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2019 236,063,279 Equity forward agreements 1,090,300 Shareowner Direct Plan 268,755 Equity-based compensation plans 101,478 Other (2,738 ) Shares outstanding, June 30, 2019 237,521,074 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. 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 agreements. During the six months ended June 30, 2019 , Alliant Energy settled $48 million under the forward sale agreements by delivering 1,090,300 shares of newly issued Alliant Energy common stock at a forward sale price of $44.13 per share. Alliant Energy used the net proceeds from the settlement for general corporate purposes. As of June 30, 2019 , 559,597 shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements. In July 2019, Alliant Energy settled $66 million under the forward sale agreements by delivering 1,500,000 shares of newly issued Alliant Energy common stock at a forward sale price of $44.06 per share, and used the net proceeds for general corporate purposes. Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $2.4 $2,100.0 $2,587.3 $2.4 ($9.7 ) $200.0 $4,882.4 Net income attributable to Alliant Energy common shareowners 94.6 94.6 Common stock dividends ($0.355 per share) (84.1 ) (84.1 ) Shareowner Direct Plan issuances 6.0 6.0 Equity-based compensation plans and other 2.4 (0.3 ) 2.1 Other comprehensive loss, net of tax (1.4 ) (1.4 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Three Months Ended June 30, 2018 Beginning balance, April 1 $2.3 $1,851.4 $2,389.4 ($0.5 ) ($11.1 ) $200.0 $4,431.5 Net income attributable to Alliant Energy common shareowners 100.4 100.4 Common stock dividends ($0.335 per share) (77.3 ) (77.3 ) At-the-market offering program and Shareowner Direct Plan issuances 93.8 93.8 Equity-based compensation plans and other 2.0 (0.3 ) 1.7 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $2.4 $2,045.5 $2,545.9 $1.7 ($9.8 ) $200.0 $4,785.7 Net income attributable to Alliant Energy common shareowners 219.7 219.7 Common stock dividends ($0.71 per share) (167.8 ) (167.8 ) Equity forward settlements and Shareowner Direct Plan issuances 60.6 60.6 Equity-based compensation plans and other 2.3 (0.2 ) 2.1 Other comprehensive loss, net of tax (0.7 ) (0.7 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Six Months Ended June 30, 2018 Beginning balance, January 1 $2.3 $1,845.5 $2,346.0 ($0.5 ) ($11.1 ) $200.0 $4,382.2 Net income attributable to Alliant Energy common shareowners 221.3 221.3 Common stock dividends ($0.67 per share) (154.8 ) (154.8 ) At-the-market offering program and Shareowner Direct Plan issuances 100.1 100.1 Equity-based compensation plans and other 1.6 (0.3 ) 1.3 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $33.4 $2,322.8 $785.8 $200.0 $3,342.0 Earnings available for common stock 45.0 45.0 Common stock dividends (41.9 ) (41.9 ) Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Three Months Ended June 30, 2018 Beginning balance, April 1 $33.4 $1,797.8 $683.3 $200.0 $2,714.5 Earnings available for common stock 51.7 51.7 Common stock dividends (42.1 ) (42.1 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $33.4 $2,222.8 $774.5 $200.0 $3,230.7 Earnings available for common stock 98.3 98.3 Common stock dividends (83.9 ) (83.9 ) Capital contributions from parent 100.0 100.0 Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Six Months Ended June 30, 2018 Beginning balance, January 1 $33.4 $1,797.8 $678.5 $200.0 $2,709.7 Earnings available for common stock 98.4 98.4 Common stock dividends (84.0 ) (84.0 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $66.2 $1,309.0 $804.0 $2,179.2 Earnings available for common stock 42.0 42.0 Common stock dividends (36.0 ) (36.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Three Months Ended June 30, 2018 Beginning balance, April 1 $66.2 $1,109.0 $725.3 $1,900.5 Earnings available for common stock 39.8 39.8 Common stock dividends (35.1 ) (35.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $66.2 $1,309.0 $774.3 $2,149.5 Earnings available for common stock 107.7 107.7 Common stock dividends (72.0 ) (72.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Six Months Ended June 30, 2018 Beginning balance, January 1 $66.2 $1,109.0 $706.3 $1,881.5 Earnings available for common stock 93.8 93.8 Common stock dividends (70.1 ) (70.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 Comprehensive Income - For the three and six months ended June 30, 2019 and 2018 , Alliant Energy’s other comprehensive income was not material; 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. For the three and six months ended June 30, 2019 and 2018 , 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]
Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2019 236,063,279 Equity forward agreements 1,090,300 Shareowner Direct Plan 268,755 Equity-based compensation plans 101,478 Other (2,738 ) Shares outstanding, June 30, 2019 237,521,074 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. 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 agreements. During the six months ended June 30, 2019 , Alliant Energy settled $48 million under the forward sale agreements by delivering 1,090,300 shares of newly issued Alliant Energy common stock at a forward sale price of $44.13 per share. Alliant Energy used the net proceeds from the settlement for general corporate purposes. As of June 30, 2019 , 559,597 shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements. In July 2019, Alliant Energy settled $66 million under the forward sale agreements by delivering 1,500,000 shares of newly issued Alliant Energy common stock at a forward sale price of $44.06 per share, and used the net proceeds for general corporate purposes. Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $2.4 $2,100.0 $2,587.3 $2.4 ($9.7 ) $200.0 $4,882.4 Net income attributable to Alliant Energy common shareowners 94.6 94.6 Common stock dividends ($0.355 per share) (84.1 ) (84.1 ) Shareowner Direct Plan issuances 6.0 6.0 Equity-based compensation plans and other 2.4 (0.3 ) 2.1 Other comprehensive loss, net of tax (1.4 ) (1.4 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Three Months Ended June 30, 2018 Beginning balance, April 1 $2.3 $1,851.4 $2,389.4 ($0.5 ) ($11.1 ) $200.0 $4,431.5 Net income attributable to Alliant Energy common shareowners 100.4 100.4 Common stock dividends ($0.335 per share) (77.3 ) (77.3 ) At-the-market offering program and Shareowner Direct Plan issuances 93.8 93.8 Equity-based compensation plans and other 2.0 (0.3 ) 1.7 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $2.4 $2,045.5 $2,545.9 $1.7 ($9.8 ) $200.0 $4,785.7 Net income attributable to Alliant Energy common shareowners 219.7 219.7 Common stock dividends ($0.71 per share) (167.8 ) (167.8 ) Equity forward settlements and Shareowner Direct Plan issuances 60.6 60.6 Equity-based compensation plans and other 2.3 (0.2 ) 2.1 Other comprehensive loss, net of tax (0.7 ) (0.7 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Six Months Ended June 30, 2018 Beginning balance, January 1 $2.3 $1,845.5 $2,346.0 ($0.5 ) ($11.1 ) $200.0 $4,382.2 Net income attributable to Alliant Energy common shareowners 221.3 221.3 Common stock dividends ($0.67 per share) (154.8 ) (154.8 ) At-the-market offering program and Shareowner Direct Plan issuances 100.1 100.1 Equity-based compensation plans and other 1.6 (0.3 ) 1.3 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $33.4 $2,322.8 $785.8 $200.0 $3,342.0 Earnings available for common stock 45.0 45.0 Common stock dividends (41.9 ) (41.9 ) Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Three Months Ended June 30, 2018 Beginning balance, April 1 $33.4 $1,797.8 $683.3 $200.0 $2,714.5 Earnings available for common stock 51.7 51.7 Common stock dividends (42.1 ) (42.1 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $33.4 $2,222.8 $774.5 $200.0 $3,230.7 Earnings available for common stock 98.3 98.3 Common stock dividends (83.9 ) (83.9 ) Capital contributions from parent 100.0 100.0 Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Six Months Ended June 30, 2018 Beginning balance, January 1 $33.4 $1,797.8 $678.5 $200.0 $2,709.7 Earnings available for common stock 98.4 98.4 Common stock dividends (84.0 ) (84.0 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $66.2 $1,309.0 $804.0 $2,179.2 Earnings available for common stock 42.0 42.0 Common stock dividends (36.0 ) (36.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Three Months Ended June 30, 2018 Beginning balance, April 1 $66.2 $1,109.0 $725.3 $1,900.5 Earnings available for common stock 39.8 39.8 Common stock dividends (35.1 ) (35.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $66.2 $1,309.0 $774.3 $2,149.5 Earnings available for common stock 107.7 107.7 Common stock dividends (72.0 ) (72.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Six Months Ended June 30, 2018 Beginning balance, January 1 $66.2 $1,109.0 $706.3 $1,881.5 Earnings available for common stock 93.8 93.8 Common stock dividends (70.1 ) (70.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 Comprehensive Income - For the three and six months ended June 30, 2019 and 2018 , Alliant Energy’s other comprehensive income was not material; 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. For the three and six months ended June 30, 2019 and 2018 , 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]
Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2019 236,063,279 Equity forward agreements 1,090,300 Shareowner Direct Plan 268,755 Equity-based compensation plans 101,478 Other (2,738 ) Shares outstanding, June 30, 2019 237,521,074 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. 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 agreements. During the six months ended June 30, 2019 , Alliant Energy settled $48 million under the forward sale agreements by delivering 1,090,300 shares of newly issued Alliant Energy common stock at a forward sale price of $44.13 per share. Alliant Energy used the net proceeds from the settlement for general corporate purposes. As of June 30, 2019 , 559,597 shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements. In July 2019, Alliant Energy settled $66 million under the forward sale agreements by delivering 1,500,000 shares of newly issued Alliant Energy common stock at a forward sale price of $44.06 per share, and used the net proceeds for general corporate purposes. Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $2.4 $2,100.0 $2,587.3 $2.4 ($9.7 ) $200.0 $4,882.4 Net income attributable to Alliant Energy common shareowners 94.6 94.6 Common stock dividends ($0.355 per share) (84.1 ) (84.1 ) Shareowner Direct Plan issuances 6.0 6.0 Equity-based compensation plans and other 2.4 (0.3 ) 2.1 Other comprehensive loss, net of tax (1.4 ) (1.4 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Three Months Ended June 30, 2018 Beginning balance, April 1 $2.3 $1,851.4 $2,389.4 ($0.5 ) ($11.1 ) $200.0 $4,431.5 Net income attributable to Alliant Energy common shareowners 100.4 100.4 Common stock dividends ($0.335 per share) (77.3 ) (77.3 ) At-the-market offering program and Shareowner Direct Plan issuances 93.8 93.8 Equity-based compensation plans and other 2.0 (0.3 ) 1.7 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $2.4 $2,045.5 $2,545.9 $1.7 ($9.8 ) $200.0 $4,785.7 Net income attributable to Alliant Energy common shareowners 219.7 219.7 Common stock dividends ($0.71 per share) (167.8 ) (167.8 ) Equity forward settlements and Shareowner Direct Plan issuances 60.6 60.6 Equity-based compensation plans and other 2.3 (0.2 ) 2.1 Other comprehensive loss, net of tax (0.7 ) (0.7 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Six Months Ended June 30, 2018 Beginning balance, January 1 $2.3 $1,845.5 $2,346.0 ($0.5 ) ($11.1 ) $200.0 $4,382.2 Net income attributable to Alliant Energy common shareowners 221.3 221.3 Common stock dividends ($0.67 per share) (154.8 ) (154.8 ) At-the-market offering program and Shareowner Direct Plan issuances 100.1 100.1 Equity-based compensation plans and other 1.6 (0.3 ) 1.3 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $33.4 $2,322.8 $785.8 $200.0 $3,342.0 Earnings available for common stock 45.0 45.0 Common stock dividends (41.9 ) (41.9 ) Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Three Months Ended June 30, 2018 Beginning balance, April 1 $33.4 $1,797.8 $683.3 $200.0 $2,714.5 Earnings available for common stock 51.7 51.7 Common stock dividends (42.1 ) (42.1 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $33.4 $2,222.8 $774.5 $200.0 $3,230.7 Earnings available for common stock 98.3 98.3 Common stock dividends (83.9 ) (83.9 ) Capital contributions from parent 100.0 100.0 Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Six Months Ended June 30, 2018 Beginning balance, January 1 $33.4 $1,797.8 $678.5 $200.0 $2,709.7 Earnings available for common stock 98.4 98.4 Common stock dividends (84.0 ) (84.0 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $66.2 $1,309.0 $804.0 $2,179.2 Earnings available for common stock 42.0 42.0 Common stock dividends (36.0 ) (36.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Three Months Ended June 30, 2018 Beginning balance, April 1 $66.2 $1,109.0 $725.3 $1,900.5 Earnings available for common stock 39.8 39.8 Common stock dividends (35.1 ) (35.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $66.2 $1,309.0 $774.3 $2,149.5 Earnings available for common stock 107.7 107.7 Common stock dividends (72.0 ) (72.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Six Months Ended June 30, 2018 Beginning balance, January 1 $66.2 $1,109.0 $706.3 $1,881.5 Earnings available for common stock 93.8 93.8 Common stock dividends (70.1 ) (70.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 Comprehensive Income - For the three and six months ended June 30, 2019 and 2018 , Alliant Energy’s other comprehensive income was not material; 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. For the three and six months ended June 30, 2019 and 2018 , 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.

Debt

Debt	6 Months Ended
	Jun. 30, 2019
Debt [Line Items]
Debt	DEBT NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year , which currently expires in August 2023. As of June 30, 2019 , the short-term borrowing capacity under the agreement totaled $1 billion ( $450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Commercial paper outstanding $390.5 $— $— Commercial paper weighted average interest rates 2.6% N/A N/A Available credit facility capacity $609.5 $250.0 $300.0 Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Maximum amount outstanding (based on daily outstanding balances) $590.2 $446.5 $— $31.4 $193.3 $109.4 Average amount outstanding (based on daily outstanding balances) $531.7 $234.5 $— $5.1 $141.6 $45.2 Weighted average interest rates 2.7% 2.2% N/A 2.3% 2.5% 1.8% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $600.6 $446.5 $50.4 $31.4 $195.1 $109.4 Average amount outstanding (based on daily outstanding balances) $515.4 $272.1 $0.3 $2.6 $139.8 $28.4 Weighted average interest rates 2.7% 2.0% 2.8% 2.3% 2.5% 1.8% NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. The senior debentures were issued as green bonds, and all of the net proceeds were allocated for the construction and development of IPL’s wind projects. In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.
IPL [Member]
Debt [Line Items]
Debt	DEBT NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year , which currently expires in August 2023. As of June 30, 2019 , the short-term borrowing capacity under the agreement totaled $1 billion ( $450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Commercial paper outstanding $390.5 $— $— Commercial paper weighted average interest rates 2.6% N/A N/A Available credit facility capacity $609.5 $250.0 $300.0 Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Maximum amount outstanding (based on daily outstanding balances) $590.2 $446.5 $— $31.4 $193.3 $109.4 Average amount outstanding (based on daily outstanding balances) $531.7 $234.5 $— $5.1 $141.6 $45.2 Weighted average interest rates 2.7% 2.2% N/A 2.3% 2.5% 1.8% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $600.6 $446.5 $50.4 $31.4 $195.1 $109.4 Average amount outstanding (based on daily outstanding balances) $515.4 $272.1 $0.3 $2.6 $139.8 $28.4 Weighted average interest rates 2.7% 2.0% 2.8% 2.3% 2.5% 1.8% NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. The senior debentures were issued as green bonds, and all of the net proceeds were allocated for the construction and development of IPL’s wind projects. In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.
WPL [Member]
Debt [Line Items]
Debt	DEBT NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year , which currently expires in August 2023. As of June 30, 2019 , the short-term borrowing capacity under the agreement totaled $1 billion ( $450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Commercial paper outstanding $390.5 $— $— Commercial paper weighted average interest rates 2.6% N/A N/A Available credit facility capacity $609.5 $250.0 $300.0 Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Maximum amount outstanding (based on daily outstanding balances) $590.2 $446.5 $— $31.4 $193.3 $109.4 Average amount outstanding (based on daily outstanding balances) $531.7 $234.5 $— $5.1 $141.6 $45.2 Weighted average interest rates 2.7% 2.2% N/A 2.3% 2.5% 1.8% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $600.6 $446.5 $50.4 $31.4 $195.1 $109.4 Average amount outstanding (based on daily outstanding balances) $515.4 $272.1 $0.3 $2.6 $139.8 $28.4 Weighted average interest rates 2.7% 2.0% 2.8% 2.3% 2.5% 1.8% NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. The senior debentures were issued as green bonds, and all of the net proceeds were allocated for the construction and development of IPL’s wind projects. In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Line Items]
Operating Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $— Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions): June 30, 2019 Property, plant and equipment, net $35 Other current liabilities $8 Finance lease obligations - Sheboygan Falls Energy Facility 56 Total finance lease liabilities $64 Remaining lease term 6 years Discount rate 11 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Depreciation expense $2 $3 Interest expense 2 4 Total finance lease expense $4 $7 Expected Maturities - As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64 Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68
IPL [Member]
Leases [Line Items]
Operating Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $— Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions): June 30, 2019 Property, plant and equipment, net $35 Other current liabilities $8 Finance lease obligations - Sheboygan Falls Energy Facility 56 Total finance lease liabilities $64 Remaining lease term 6 years Discount rate 11 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Depreciation expense $2 $3 Interest expense 2 4 Total finance lease expense $4 $7 Expected Maturities - As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64 Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68
WPL [Member]
Leases [Line Items]
Operating Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $— Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions): June 30, 2019 Property, plant and equipment, net $35 Other current liabilities $8 Finance lease obligations - Sheboygan Falls Energy Facility 56 Total finance lease liabilities $64 Remaining lease term 6 years Discount rate 11 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Depreciation expense $2 $3 Interest expense 2 4 Total finance lease expense $4 $7 Expected Maturities - As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64 Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68
Finance Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $— Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions): June 30, 2019 Property, plant and equipment, net $35 Other current liabilities $8 Finance lease obligations - Sheboygan Falls Energy Facility 56 Total finance lease liabilities $64 Remaining lease term 6 years Discount rate 11 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Depreciation expense $2 $3 Interest expense 2 4 Total finance lease expense $4 $7 Expected Maturities - As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64 Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68

Revenues

Revenues	6 Months Ended
	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	REVENUES Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $233.3 $248.3 $125.9 $139.3 $107.4 $109.0 Retail - commercial 171.3 172.3 111.4 114.2 59.9 58.1 Retail - industrial 214.2 225.4 118.4 128.8 95.8 96.6 Wholesale 41.0 43.1 14.6 13.9 26.4 29.2 Bulk power and other 31.4 37.2 22.0 25.9 9.4 11.3 Total Electric Utility 691.2 726.3 392.3 422.1 298.9 304.2 Gas Utility: Retail - residential 35.2 37.7 20.0 22.8 15.2 14.9 Retail - commercial 16.1 19.3 8.8 11.8 7.3 7.5 Retail - industrial 2.0 2.6 1.6 1.4 0.4 1.2 Transportation/other 11.9 9.0 8.0 6.2 3.9 2.8 Total Gas Utility 65.2 68.6 38.4 42.2 26.8 26.4 Other Utility: Steam 9.2 8.4 9.2 8.4 — — Other utility 1.7 2.3 1.3 2.1 0.4 0.2 Total Other Utility 10.9 10.7 10.5 10.5 0.4 0.2 Non-Utility and Other: Transportation and other 22.9 10.5 — — — — Total Non-Utility and Other 22.9 10.5 — — — — Total revenues $790.2 $816.1 $441.2 $474.8 $326.1 $330.8 Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $508.0 $507.7 $273.4 $281.5 $234.6 $226.2 Retail - commercial 352.4 346.3 228.0 225.8 124.4 120.5 Retail - industrial 422.9 427.3 234.5 243.6 188.4 183.7 Wholesale 87.5 96.9 31.5 38.2 56.0 58.7 Bulk power and other 63.8 56.8 44.7 38.7 19.1 18.1 Total Electric Utility 1,434.6 1,435.0 812.1 827.8 622.5 607.2 Gas Utility: Retail - residential 167.0 148.3 97.9 88.3 69.1 60.0 Retail - commercial 79.7 76.3 43.6 43.4 36.1 32.9 Retail - industrial 7.4 8.4 4.8 4.1 2.6 4.3 Transportation/other 26.9 21.2 16.7 14.5 10.2 6.7 Total Gas Utility 281.0 254.2 163.0 150.3 118.0 103.9 Other Utility: Steam 17.6 17.8 17.6 17.8 — — Other utility 4.4 6.1 3.6 4.7 0.8 1.4 Total Other Utility 22.0 23.9 21.2 22.5 0.8 1.4 Non-Utility and Other: Transportation and other 39.8 19.3 — — — — Total Non-Utility and Other 39.8 19.3 — — — — Total revenues $1,777.4 $1,732.4 $996.3 $1,000.6 $741.3 $712.5
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	REVENUES Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $233.3 $248.3 $125.9 $139.3 $107.4 $109.0 Retail - commercial 171.3 172.3 111.4 114.2 59.9 58.1 Retail - industrial 214.2 225.4 118.4 128.8 95.8 96.6 Wholesale 41.0 43.1 14.6 13.9 26.4 29.2 Bulk power and other 31.4 37.2 22.0 25.9 9.4 11.3 Total Electric Utility 691.2 726.3 392.3 422.1 298.9 304.2 Gas Utility: Retail - residential 35.2 37.7 20.0 22.8 15.2 14.9 Retail - commercial 16.1 19.3 8.8 11.8 7.3 7.5 Retail - industrial 2.0 2.6 1.6 1.4 0.4 1.2 Transportation/other 11.9 9.0 8.0 6.2 3.9 2.8 Total Gas Utility 65.2 68.6 38.4 42.2 26.8 26.4 Other Utility: Steam 9.2 8.4 9.2 8.4 — — Other utility 1.7 2.3 1.3 2.1 0.4 0.2 Total Other Utility 10.9 10.7 10.5 10.5 0.4 0.2 Non-Utility and Other: Transportation and other 22.9 10.5 — — — — Total Non-Utility and Other 22.9 10.5 — — — — Total revenues $790.2 $816.1 $441.2 $474.8 $326.1 $330.8 Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $508.0 $507.7 $273.4 $281.5 $234.6 $226.2 Retail - commercial 352.4 346.3 228.0 225.8 124.4 120.5 Retail - industrial 422.9 427.3 234.5 243.6 188.4 183.7 Wholesale 87.5 96.9 31.5 38.2 56.0 58.7 Bulk power and other 63.8 56.8 44.7 38.7 19.1 18.1 Total Electric Utility 1,434.6 1,435.0 812.1 827.8 622.5 607.2 Gas Utility: Retail - residential 167.0 148.3 97.9 88.3 69.1 60.0 Retail - commercial 79.7 76.3 43.6 43.4 36.1 32.9 Retail - industrial 7.4 8.4 4.8 4.1 2.6 4.3 Transportation/other 26.9 21.2 16.7 14.5 10.2 6.7 Total Gas Utility 281.0 254.2 163.0 150.3 118.0 103.9 Other Utility: Steam 17.6 17.8 17.6 17.8 — — Other utility 4.4 6.1 3.6 4.7 0.8 1.4 Total Other Utility 22.0 23.9 21.2 22.5 0.8 1.4 Non-Utility and Other: Transportation and other 39.8 19.3 — — — — Total Non-Utility and Other 39.8 19.3 — — — — Total revenues $1,777.4 $1,732.4 $996.3 $1,000.6 $741.3 $712.5
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer	REVENUES Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $233.3 $248.3 $125.9 $139.3 $107.4 $109.0 Retail - commercial 171.3 172.3 111.4 114.2 59.9 58.1 Retail - industrial 214.2 225.4 118.4 128.8 95.8 96.6 Wholesale 41.0 43.1 14.6 13.9 26.4 29.2 Bulk power and other 31.4 37.2 22.0 25.9 9.4 11.3 Total Electric Utility 691.2 726.3 392.3 422.1 298.9 304.2 Gas Utility: Retail - residential 35.2 37.7 20.0 22.8 15.2 14.9 Retail - commercial 16.1 19.3 8.8 11.8 7.3 7.5 Retail - industrial 2.0 2.6 1.6 1.4 0.4 1.2 Transportation/other 11.9 9.0 8.0 6.2 3.9 2.8 Total Gas Utility 65.2 68.6 38.4 42.2 26.8 26.4 Other Utility: Steam 9.2 8.4 9.2 8.4 — — Other utility 1.7 2.3 1.3 2.1 0.4 0.2 Total Other Utility 10.9 10.7 10.5 10.5 0.4 0.2 Non-Utility and Other: Transportation and other 22.9 10.5 — — — — Total Non-Utility and Other 22.9 10.5 — — — — Total revenues $790.2 $816.1 $441.2 $474.8 $326.1 $330.8 Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $508.0 $507.7 $273.4 $281.5 $234.6 $226.2 Retail - commercial 352.4 346.3 228.0 225.8 124.4 120.5 Retail - industrial 422.9 427.3 234.5 243.6 188.4 183.7 Wholesale 87.5 96.9 31.5 38.2 56.0 58.7 Bulk power and other 63.8 56.8 44.7 38.7 19.1 18.1 Total Electric Utility 1,434.6 1,435.0 812.1 827.8 622.5 607.2 Gas Utility: Retail - residential 167.0 148.3 97.9 88.3 69.1 60.0 Retail - commercial 79.7 76.3 43.6 43.4 36.1 32.9 Retail - industrial 7.4 8.4 4.8 4.1 2.6 4.3 Transportation/other 26.9 21.2 16.7 14.5 10.2 6.7 Total Gas Utility 281.0 254.2 163.0 150.3 118.0 103.9 Other Utility: Steam 17.6 17.8 17.6 17.8 — — Other utility 4.4 6.1 3.6 4.7 0.8 1.4 Total Other Utility 22.0 23.9 21.2 22.5 0.8 1.4 Non-Utility and Other: Transportation and other 39.8 19.3 — — — — Total Non-Utility and Other 39.8 19.3 — — — — Total revenues $1,777.4 $1,732.4 $996.3 $1,000.6 $741.3 $712.5

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes. Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.5 6.5 8.3 7.0 6.2 6.2 Production tax credits (8.5 ) (5.4 ) (13.2 ) (5.3 ) (4.2 ) (6.8 ) Effect of rate-making on property-related differences (6.2 ) (6.7 ) (10.1 ) (11.5 ) (2.7 ) (2.7 ) Amortization of excess deferred taxes (1.3 ) (0.4 ) (0.4 ) — (2.3 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.1 ) (1.4 ) (4.3 ) — — Other items, net (1.5 ) (1.2 ) (0.4 ) (2.8 ) (2.5 ) (4.1 ) Overall income tax rate 10.3 % 11.7 % 3.8 % 4.1 % 15.5 % 13.5 % Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.2 7.1 8.1 7.7 6.2 6.2 Production tax credits (8.9 ) (5.5 ) (13.6 ) (5.3 ) (4.6 ) (6.7 ) Effect of rate-making on property-related differences (6.0 ) (7.2 ) (9.6 ) (12.4 ) (2.4 ) (2.5 ) Amortization of excess deferred taxes (1.1 ) (0.4 ) (0.3 ) — (1.8 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.2 ) (1.4 ) (4.5 ) — — Other items, net (1.0 ) (1.0 ) (0.5 ) (1.5 ) (1.2 ) (1.9 ) Overall income tax rate 10.5 % 11.8 % 3.7 % 5.0 % 17.2 % 16.0 % Deferred Tax Assets and Liabilities - Carryforwards - At June 30, 2019 , carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2031-2037 $760 $550 $122 State net operating losses 2019-2039 764 13 2 Federal tax credits 2022-2039 325 152 154
IPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes. Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.5 6.5 8.3 7.0 6.2 6.2 Production tax credits (8.5 ) (5.4 ) (13.2 ) (5.3 ) (4.2 ) (6.8 ) Effect of rate-making on property-related differences (6.2 ) (6.7 ) (10.1 ) (11.5 ) (2.7 ) (2.7 ) Amortization of excess deferred taxes (1.3 ) (0.4 ) (0.4 ) — (2.3 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.1 ) (1.4 ) (4.3 ) — — Other items, net (1.5 ) (1.2 ) (0.4 ) (2.8 ) (2.5 ) (4.1 ) Overall income tax rate 10.3 % 11.7 % 3.8 % 4.1 % 15.5 % 13.5 % Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.2 7.1 8.1 7.7 6.2 6.2 Production tax credits (8.9 ) (5.5 ) (13.6 ) (5.3 ) (4.6 ) (6.7 ) Effect of rate-making on property-related differences (6.0 ) (7.2 ) (9.6 ) (12.4 ) (2.4 ) (2.5 ) Amortization of excess deferred taxes (1.1 ) (0.4 ) (0.3 ) — (1.8 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.2 ) (1.4 ) (4.5 ) — — Other items, net (1.0 ) (1.0 ) (0.5 ) (1.5 ) (1.2 ) (1.9 ) Overall income tax rate 10.5 % 11.8 % 3.7 % 5.0 % 17.2 % 16.0 % Deferred Tax Assets and Liabilities - Carryforwards - At June 30, 2019 , carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2031-2037 $760 $550 $122 State net operating losses 2019-2039 764 13 2 Federal tax credits 2022-2039 325 152 154
WPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes. Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.5 6.5 8.3 7.0 6.2 6.2 Production tax credits (8.5 ) (5.4 ) (13.2 ) (5.3 ) (4.2 ) (6.8 ) Effect of rate-making on property-related differences (6.2 ) (6.7 ) (10.1 ) (11.5 ) (2.7 ) (2.7 ) Amortization of excess deferred taxes (1.3 ) (0.4 ) (0.4 ) — (2.3 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.1 ) (1.4 ) (4.3 ) — — Other items, net (1.5 ) (1.2 ) (0.4 ) (2.8 ) (2.5 ) (4.1 ) Overall income tax rate 10.3 % 11.7 % 3.8 % 4.1 % 15.5 % 13.5 % Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.2 7.1 8.1 7.7 6.2 6.2 Production tax credits (8.9 ) (5.5 ) (13.6 ) (5.3 ) (4.6 ) (6.7 ) Effect of rate-making on property-related differences (6.0 ) (7.2 ) (9.6 ) (12.4 ) (2.4 ) (2.5 ) Amortization of excess deferred taxes (1.1 ) (0.4 ) (0.3 ) — (1.8 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.2 ) (1.4 ) (4.5 ) — — Other items, net (1.0 ) (1.0 ) (0.5 ) (1.5 ) (1.2 ) (1.9 ) Overall income tax rate 10.5 % 11.8 % 3.7 % 5.0 % 17.2 % 16.0 % Deferred Tax Assets and Liabilities - Carryforwards - At June 30, 2019 , carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2031-2037 $760 $550 $122 State net operating losses 2019-2039 764 13 2 Federal tax credits 2022-2039 325 152 154

Benefit Plans

Benefit Plans	6 Months Ended
	Jun. 30, 2019
Benefit Plans	BENEFIT PLANS NOTE 10(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and six months ended June 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months Alliant Energy 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $2.4 $3.0 $4.8 $6.0 $0.9 $1.0 $1.7 $2.1 Interest cost 12.4 11.7 24.9 23.4 2.1 1.9 4.2 3.8 Expected return on plan assets (15.0 ) (17.5 ) (30.0 ) (34.9 ) (1.3 ) (1.5 ) (2.5 ) (3.0 ) Amortization of prior service credit (0.1 ) (0.1 ) (0.3 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 9.1 8.8 18.2 17.6 0.8 0.9 1.6 1.7 $8.8 $5.9 $17.6 $11.8 $2.4 $2.2 $4.9 $4.5 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $1.5 $1.9 $3.0 $3.7 $0.4 $0.5 $0.7 $0.9 Interest cost 5.7 5.4 11.4 10.7 0.9 0.8 1.7 1.6 Expected return on plan assets (7.1 ) (8.2 ) (14.1 ) (16.3 ) (0.9 ) (1.1 ) (1.8 ) (2.2 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) — — — — Amortization of actuarial loss 4.0 3.8 7.9 7.5 0.3 0.3 0.7 0.6 $4.1 $2.8 $8.1 $5.5 $0.7 $0.5 $1.3 $0.9 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $0.8 $1.1 $1.7 $2.2 $0.3 $0.4 $0.6 $0.8 Interest cost 5.4 5.1 10.8 10.1 0.9 0.7 1.7 1.5 Expected return on plan assets (6.6 ) (7.6 ) (13.1 ) (15.2 ) (0.2 ) (0.1 ) (0.3 ) (0.3 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 4.4 4.3 8.8 8.6 0.4 0.5 0.8 1.0 $4.0 $2.8 $8.1 $5.6 $1.3 $1.4 $2.7 $2.9 NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 Compensation expense $3.4 $5.1 $8.1 $8.4 $1.9 $2.8 $4.5 $4.6 $1.4 $2.1 $3.2 $3.4 Income tax benefits 1.0 1.5 2.3 2.4 0.5 0.9 1.3 1.4 0.4 0.5 0.9 0.9 As of June 30, 2019 , Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $10.3 million , $5.7 million and $4.2 million , respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years. In the first quarter of 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3 -year performance period. In the first quarter of 2019, 80,837 performance shares were granted with a grant date fair value of $46.35 . The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3 -year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3 - year time-vesting period. In the first quarter of 2019, 80,837 performance restricted stock units and 95,938 restricted stock units were granted with a grant date fair value of $45.63 , which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of June 30, 2019 , an immaterial amount of shares was included in the calculation of diluted EPS related to the nonvested equity awards.
IPL [Member]
Benefit Plans	BENEFIT PLANS NOTE 10(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and six months ended June 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months Alliant Energy 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $2.4 $3.0 $4.8 $6.0 $0.9 $1.0 $1.7 $2.1 Interest cost 12.4 11.7 24.9 23.4 2.1 1.9 4.2 3.8 Expected return on plan assets (15.0 ) (17.5 ) (30.0 ) (34.9 ) (1.3 ) (1.5 ) (2.5 ) (3.0 ) Amortization of prior service credit (0.1 ) (0.1 ) (0.3 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 9.1 8.8 18.2 17.6 0.8 0.9 1.6 1.7 $8.8 $5.9 $17.6 $11.8 $2.4 $2.2 $4.9 $4.5 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $1.5 $1.9 $3.0 $3.7 $0.4 $0.5 $0.7 $0.9 Interest cost 5.7 5.4 11.4 10.7 0.9 0.8 1.7 1.6 Expected return on plan assets (7.1 ) (8.2 ) (14.1 ) (16.3 ) (0.9 ) (1.1 ) (1.8 ) (2.2 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) — — — — Amortization of actuarial loss 4.0 3.8 7.9 7.5 0.3 0.3 0.7 0.6 $4.1 $2.8 $8.1 $5.5 $0.7 $0.5 $1.3 $0.9 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $0.8 $1.1 $1.7 $2.2 $0.3 $0.4 $0.6 $0.8 Interest cost 5.4 5.1 10.8 10.1 0.9 0.7 1.7 1.5 Expected return on plan assets (6.6 ) (7.6 ) (13.1 ) (15.2 ) (0.2 ) (0.1 ) (0.3 ) (0.3 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 4.4 4.3 8.8 8.6 0.4 0.5 0.8 1.0 $4.0 $2.8 $8.1 $5.6 $1.3 $1.4 $2.7 $2.9 NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 Compensation expense $3.4 $5.1 $8.1 $8.4 $1.9 $2.8 $4.5 $4.6 $1.4 $2.1 $3.2 $3.4 Income tax benefits 1.0 1.5 2.3 2.4 0.5 0.9 1.3 1.4 0.4 0.5 0.9 0.9 As of June 30, 2019 , Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $10.3 million , $5.7 million and $4.2 million , respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years. In the first quarter of 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3 -year performance period. In the first quarter of 2019, 80,837 performance shares were granted with a grant date fair value of $46.35 . The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3 -year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3 - year time-vesting period. In the first quarter of 2019, 80,837 performance restricted stock units and 95,938 restricted stock units were granted with a grant date fair value of $45.63 , which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of June 30, 2019 , an immaterial amount of shares was included in the calculation of diluted EPS related to the nonvested equity awards.
WPL [Member]
Benefit Plans	BENEFIT PLANS NOTE 10(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and six months ended June 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months Alliant Energy 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $2.4 $3.0 $4.8 $6.0 $0.9 $1.0 $1.7 $2.1 Interest cost 12.4 11.7 24.9 23.4 2.1 1.9 4.2 3.8 Expected return on plan assets (15.0 ) (17.5 ) (30.0 ) (34.9 ) (1.3 ) (1.5 ) (2.5 ) (3.0 ) Amortization of prior service credit (0.1 ) (0.1 ) (0.3 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 9.1 8.8 18.2 17.6 0.8 0.9 1.6 1.7 $8.8 $5.9 $17.6 $11.8 $2.4 $2.2 $4.9 $4.5 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $1.5 $1.9 $3.0 $3.7 $0.4 $0.5 $0.7 $0.9 Interest cost 5.7 5.4 11.4 10.7 0.9 0.8 1.7 1.6 Expected return on plan assets (7.1 ) (8.2 ) (14.1 ) (16.3 ) (0.9 ) (1.1 ) (1.8 ) (2.2 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) — — — — Amortization of actuarial loss 4.0 3.8 7.9 7.5 0.3 0.3 0.7 0.6 $4.1 $2.8 $8.1 $5.5 $0.7 $0.5 $1.3 $0.9 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $0.8 $1.1 $1.7 $2.2 $0.3 $0.4 $0.6 $0.8 Interest cost 5.4 5.1 10.8 10.1 0.9 0.7 1.7 1.5 Expected return on plan assets (6.6 ) (7.6 ) (13.1 ) (15.2 ) (0.2 ) (0.1 ) (0.3 ) (0.3 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 4.4 4.3 8.8 8.6 0.4 0.5 0.8 1.0 $4.0 $2.8 $8.1 $5.6 $1.3 $1.4 $2.7 $2.9 NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 Compensation expense $3.4 $5.1 $8.1 $8.4 $1.9 $2.8 $4.5 $4.6 $1.4 $2.1 $3.2 $3.4 Income tax benefits 1.0 1.5 2.3 2.4 0.5 0.9 1.3 1.4 0.4 0.5 0.9 0.9 As of June 30, 2019 , Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $10.3 million , $5.7 million and $4.2 million , respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years. In the first quarter of 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3 -year performance period. In the first quarter of 2019, 80,837 performance shares were granted with a grant date fair value of $46.35 . The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3 -year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3 - year time-vesting period. In the first quarter of 2019, 80,837 performance restricted stock units and 95,938 restricted stock units were granted with a grant date fair value of $45.63 , which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of June 30, 2019 , an immaterial amount of shares was included in the calculation of diluted EPS related to the nonvested equity awards.

Asset Retirement Obligations

Asset Retirement Obligations	6 Months Ended
	Jun. 30, 2019
Asset Retirement Obligations [Line Items]
Asset Retirement Obligations	ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the six months ended June 30, 2019 is as follows (in millions): Alliant Energy IPL Balance, January 1 $177.5 $118.3 Revisions in estimated cash flows (2.2 ) (2.2 ) Liabilities settled (1.4 ) (1.2 ) Liabilities incurred (a) 25.9 25.9 Accretion expense 3.4 2.2 Balance, June 30 $203.2 $143.0 (a) During the six months ended June 30 , 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
IPL [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligations	ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the six months ended June 30, 2019 is as follows (in millions): Alliant Energy IPL Balance, January 1 $177.5 $118.3 Revisions in estimated cash flows (2.2 ) (2.2 ) Liabilities settled (1.4 ) (1.2 ) Liabilities incurred (a) 25.9 25.9 Accretion expense 3.4 2.2 Balance, June 30 $203.2 $143.0 (a) During the six months ended June 30 , 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2019
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of June 30, 2019 , gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 24,229 2019-2020 163,808 2019-2026 8,027 2019-2021 6,552 2019-2021 IPL 11,721 2019-2020 75,276 2019-2026 3,587 2019-2021 — — WPL 12,508 2019-2020 88,532 2019-2026 4,440 2019-2021 6,552 2019-2021 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $18.4 $24.6 $12.0 $16.1 $6.4 $8.5 Non-current derivative assets 3.5 3.7 1.9 1.6 1.6 2.1 Current derivative liabilities 12.9 5.6 5.8 3.1 7.1 2.5 Non-current derivative liabilities 15.1 17.7 6.4 8.1 8.7 9.6 Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At June 30, 2019 and December 31, 2018 , the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at June 30, 2019 and December 31, 2018 . Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
IPL [Member]
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of June 30, 2019 , gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 24,229 2019-2020 163,808 2019-2026 8,027 2019-2021 6,552 2019-2021 IPL 11,721 2019-2020 75,276 2019-2026 3,587 2019-2021 — — WPL 12,508 2019-2020 88,532 2019-2026 4,440 2019-2021 6,552 2019-2021 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $18.4 $24.6 $12.0 $16.1 $6.4 $8.5 Non-current derivative assets 3.5 3.7 1.9 1.6 1.6 2.1 Current derivative liabilities 12.9 5.6 5.8 3.1 7.1 2.5 Non-current derivative liabilities 15.1 17.7 6.4 8.1 8.7 9.6 Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At June 30, 2019 and December 31, 2018 , the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at June 30, 2019 and December 31, 2018 . Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
WPL [Member]
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of June 30, 2019 , gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 24,229 2019-2020 163,808 2019-2026 8,027 2019-2021 6,552 2019-2021 IPL 11,721 2019-2020 75,276 2019-2026 3,587 2019-2021 — — WPL 12,508 2019-2020 88,532 2019-2026 4,440 2019-2021 6,552 2019-2021 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $18.4 $24.6 $12.0 $16.1 $6.4 $8.5 Non-current derivative assets 3.5 3.7 1.9 1.6 1.6 2.1 Current derivative liabilities 12.9 5.6 5.8 3.1 7.1 2.5 Non-current derivative liabilities 15.1 17.7 6.4 8.1 8.7 9.6 Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At June 30, 2019 and December 31, 2018 , the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at June 30, 2019 and December 31, 2018 . Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $161.8 $161.8 $— $— $161.8 $— $— $— $— $— Derivatives 21.9 — 8.2 13.7 21.9 28.3 — 8.9 19.4 28.3 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 28.0 — 27.5 0.5 28.0 23.3 — 16.1 7.2 23.3 Long-term debt (incl. current maturities) 6,144.9 — 6,788.8 2.1 6,790.9 5,502.8 — 5,858.4 2.4 5,860.8 IPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $13.9 $— $4.1 $9.8 $13.9 $17.7 $— $4.0 $13.7 $17.7 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 12.2 — 11.7 0.5 12.2 11.2 — 6.5 4.7 11.2 Long-term debt 2,850.5 — 3,135.3 — 3,135.3 2,552.3 — 2,691.2 — 2,691.2 WPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $160.4 $160.4 $— $— $160.4 $— $— $— $— $— Derivatives 8.0 — 4.1 3.9 8.0 10.6 — 4.9 5.7 10.6 Liabilities: Derivatives 15.8 — 15.8 — 15.8 12.1 — 9.6 2.5 12.1 Long-term debt (incl. current maturities) 2,181.8 — 2,498.2 — 2,498.2 1,834.9 — 2,043.7 — 2,043.7 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.4 ($29.4 ) $178.3 $120.9 Total net losses included in changes in net assets (realized/unrealized) (0.1 ) (0.2 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Settlements (a) (4.8 ) (7.8 ) 36.3 87.4 Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 $— ($0.1 ) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $12.2 ($12.2 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (5.7 ) (10.0 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Sales (0.2 ) — — — Settlements (a) (10.8 ) (15.2 ) 95.2 (13.8 ) Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($2.6 ) ($9.7 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.6 ($15.4 ) $178.3 $120.9 Total net gains (losses) included in changes in net assets (realized/unrealized) 0.4 (1.6 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Settlements (a) (3.7 ) (6.4 ) 36.3 87.4 Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 $0.5 ($1.6 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $9.0 ($1.4 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (2.8 ) (9.2 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Sales (0.1 ) — — — Settlements (a) (8.8 ) (12.8 ) 95.2 (13.8 ) Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($0.9 ) ($9.0 ) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2019 2018 Beginning balance, April 1 ($0.2 ) ($14.0 ) Total net gains (losses) included in changes in net assets (realized/unrealized) (0.5 ) 1.4 Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Settlements (1.1 ) (1.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 ($0.5 ) $1.5 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2019 2018 Beginning balance, January 1 $3.2 ($10.8 ) Total net losses included in changes in net assets (realized/unrealized) (2.9 ) (0.8 ) Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Sales (0.1 ) — Settlements (2.0 ) (2.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($1.7 ) ($0.7 ) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2019 $2.4 $10.8 $1.4 $7.9 $1.0 $2.9 December 31, 2018 3.2 9.0 1.8 7.2 1.4 1.8
IPL [Member]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $161.8 $161.8 $— $— $161.8 $— $— $— $— $— Derivatives 21.9 — 8.2 13.7 21.9 28.3 — 8.9 19.4 28.3 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 28.0 — 27.5 0.5 28.0 23.3 — 16.1 7.2 23.3 Long-term debt (incl. current maturities) 6,144.9 — 6,788.8 2.1 6,790.9 5,502.8 — 5,858.4 2.4 5,860.8 IPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $13.9 $— $4.1 $9.8 $13.9 $17.7 $— $4.0 $13.7 $17.7 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 12.2 — 11.7 0.5 12.2 11.2 — 6.5 4.7 11.2 Long-term debt 2,850.5 — 3,135.3 — 3,135.3 2,552.3 — 2,691.2 — 2,691.2 WPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $160.4 $160.4 $— $— $160.4 $— $— $— $— $— Derivatives 8.0 — 4.1 3.9 8.0 10.6 — 4.9 5.7 10.6 Liabilities: Derivatives 15.8 — 15.8 — 15.8 12.1 — 9.6 2.5 12.1 Long-term debt (incl. current maturities) 2,181.8 — 2,498.2 — 2,498.2 1,834.9 — 2,043.7 — 2,043.7 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.4 ($29.4 ) $178.3 $120.9 Total net losses included in changes in net assets (realized/unrealized) (0.1 ) (0.2 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Settlements (a) (4.8 ) (7.8 ) 36.3 87.4 Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 $— ($0.1 ) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $12.2 ($12.2 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (5.7 ) (10.0 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Sales (0.2 ) — — — Settlements (a) (10.8 ) (15.2 ) 95.2 (13.8 ) Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($2.6 ) ($9.7 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.6 ($15.4 ) $178.3 $120.9 Total net gains (losses) included in changes in net assets (realized/unrealized) 0.4 (1.6 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Settlements (a) (3.7 ) (6.4 ) 36.3 87.4 Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 $0.5 ($1.6 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $9.0 ($1.4 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (2.8 ) (9.2 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Sales (0.1 ) — — — Settlements (a) (8.8 ) (12.8 ) 95.2 (13.8 ) Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($0.9 ) ($9.0 ) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2019 2018 Beginning balance, April 1 ($0.2 ) ($14.0 ) Total net gains (losses) included in changes in net assets (realized/unrealized) (0.5 ) 1.4 Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Settlements (1.1 ) (1.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 ($0.5 ) $1.5 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2019 2018 Beginning balance, January 1 $3.2 ($10.8 ) Total net losses included in changes in net assets (realized/unrealized) (2.9 ) (0.8 ) Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Sales (0.1 ) — Settlements (2.0 ) (2.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($1.7 ) ($0.7 ) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2019 $2.4 $10.8 $1.4 $7.9 $1.0 $2.9 December 31, 2018 3.2 9.0 1.8 7.2 1.4 1.8
WPL [Member]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $161.8 $161.8 $— $— $161.8 $— $— $— $— $— Derivatives 21.9 — 8.2 13.7 21.9 28.3 — 8.9 19.4 28.3 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 28.0 — 27.5 0.5 28.0 23.3 — 16.1 7.2 23.3 Long-term debt (incl. current maturities) 6,144.9 — 6,788.8 2.1 6,790.9 5,502.8 — 5,858.4 2.4 5,860.8 IPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $13.9 $— $4.1 $9.8 $13.9 $17.7 $— $4.0 $13.7 $17.7 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 12.2 — 11.7 0.5 12.2 11.2 — 6.5 4.7 11.2 Long-term debt 2,850.5 — 3,135.3 — 3,135.3 2,552.3 — 2,691.2 — 2,691.2 WPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $160.4 $160.4 $— $— $160.4 $— $— $— $— $— Derivatives 8.0 — 4.1 3.9 8.0 10.6 — 4.9 5.7 10.6 Liabilities: Derivatives 15.8 — 15.8 — 15.8 12.1 — 9.6 2.5 12.1 Long-term debt (incl. current maturities) 2,181.8 — 2,498.2 — 2,498.2 1,834.9 — 2,043.7 — 2,043.7 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.4 ($29.4 ) $178.3 $120.9 Total net losses included in changes in net assets (realized/unrealized) (0.1 ) (0.2 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Settlements (a) (4.8 ) (7.8 ) 36.3 87.4 Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 $— ($0.1 ) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $12.2 ($12.2 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (5.7 ) (10.0 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Sales (0.2 ) — — — Settlements (a) (10.8 ) (15.2 ) 95.2 (13.8 ) Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($2.6 ) ($9.7 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.6 ($15.4 ) $178.3 $120.9 Total net gains (losses) included in changes in net assets (realized/unrealized) 0.4 (1.6 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Settlements (a) (3.7 ) (6.4 ) 36.3 87.4 Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 $0.5 ($1.6 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $9.0 ($1.4 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (2.8 ) (9.2 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Sales (0.1 ) — — — Settlements (a) (8.8 ) (12.8 ) 95.2 (13.8 ) Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($0.9 ) ($9.0 ) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2019 2018 Beginning balance, April 1 ($0.2 ) ($14.0 ) Total net gains (losses) included in changes in net assets (realized/unrealized) (0.5 ) 1.4 Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Settlements (1.1 ) (1.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 ($0.5 ) $1.5 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2019 2018 Beginning balance, January 1 $3.2 ($10.8 ) Total net losses included in changes in net assets (realized/unrealized) (2.9 ) (0.8 ) Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Sales (0.1 ) — Settlements (2.0 ) (2.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($1.7 ) ($0.7 ) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2019 $2.4 $10.8 $1.4 $7.9 $1.0 $2.9 December 31, 2018 3.2 9.0 1.8 7.2 1.4 1.8

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s projects include the expansion of wind generation. WPL’s projects include the West Riverside Energy Center. At June 30, 2019 , Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $268 million , $237 million and $31 million , respectively. NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At June 30, 2019 , the related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Purchased power (a) $184 $183 $1 Natural gas 925 460 465 Coal (b) 130 81 49 Other (c) 88 49 28 $1,327 $773 $543 (a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million . (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change. (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 . NOTE 14(c) Guarantees and Indemnifications - Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of June 30, 2019 , the present value of the abandonment obligations is estimated at $37 million . Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of June 30, 2019 and December 31, 2018 . Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $90 million as of June 30, 2019 and will reduce annually until expiring in July 2047 . Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031 , subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of June 30, 2019 and December 31, 2018 . IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of June 30, 2019 and December 31, 2018 . The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020 . NOTE 14(d) Environmental Matters - Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At June 30, 2019 , estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At June 30, 2019 , such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $15 - $31 $12 - $26 Current and non-current environmental liabilities 19 16 IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers. Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act. Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters. NOTE 14(e) Collective Bargaining Agreements - At June 30, 2019 , employees covered by collective bargaining agreements represented 54% , 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. The parties continue to negotiate, and signed an extension that continues until a tentative agreement is ratified or either party gives 30 days’ notice to cancel the extension. Alliant Energy and WPL are currently unable to predict the outcome of this matter.
IPL [Member]
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s projects include the expansion of wind generation. WPL’s projects include the West Riverside Energy Center. At June 30, 2019 , Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $268 million , $237 million and $31 million , respectively. NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At June 30, 2019 , the related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Purchased power (a) $184 $183 $1 Natural gas 925 460 465 Coal (b) 130 81 49 Other (c) 88 49 28 $1,327 $773 $543 (a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million . (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change. (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 . NOTE 14(c) Guarantees and Indemnifications - Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of June 30, 2019 , the present value of the abandonment obligations is estimated at $37 million . Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of June 30, 2019 and December 31, 2018 . Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $90 million as of June 30, 2019 and will reduce annually until expiring in July 2047 . Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031 , subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of June 30, 2019 and December 31, 2018 . IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of June 30, 2019 and December 31, 2018 . The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020 . NOTE 14(d) Environmental Matters - Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At June 30, 2019 , estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At June 30, 2019 , such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $15 - $31 $12 - $26 Current and non-current environmental liabilities 19 16 IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers. Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act. Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters. NOTE 14(e) Collective Bargaining Agreements - At June 30, 2019 , employees covered by collective bargaining agreements represented 54% , 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. The parties continue to negotiate, and signed an extension that continues until a tentative agreement is ratified or either party gives 30 days’ notice to cancel the extension. Alliant Energy and WPL are currently unable to predict the outcome of this matter.
WPL [Member]
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s projects include the expansion of wind generation. WPL’s projects include the West Riverside Energy Center. At June 30, 2019 , Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $268 million , $237 million and $31 million , respectively. NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At June 30, 2019 , the related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Purchased power (a) $184 $183 $1 Natural gas 925 460 465 Coal (b) 130 81 49 Other (c) 88 49 28 $1,327 $773 $543 (a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million . (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change. (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 . NOTE 14(c) Guarantees and Indemnifications - Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of June 30, 2019 , the present value of the abandonment obligations is estimated at $37 million . Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of June 30, 2019 and December 31, 2018 . Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $90 million as of June 30, 2019 and will reduce annually until expiring in July 2047 . Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031 , subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of June 30, 2019 and December 31, 2018 . IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of June 30, 2019 and December 31, 2018 . The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020 . NOTE 14(d) Environmental Matters - Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At June 30, 2019 , estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At June 30, 2019 , such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $15 - $31 $12 - $26 Current and non-current environmental liabilities 19 16 IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers. Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act. Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters. NOTE 14(e) Collective Bargaining Agreements - At June 30, 2019 , employees covered by collective bargaining agreements represented 54% , 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. The parties continue to negotiate, and signed an extension that continues until a tentative agreement is ratified or either party gives 30 days’ notice to cancel the extension. Alliant Energy and WPL are currently unable to predict the outcome of this matter.

Segments Of Business

Segments Of Business	6 Months Ended
	Jun. 30, 2019
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations. ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended June 30, 2019 Revenues $691.2 $65.2 $10.9 $767.3 $22.9 $790.2 Operating income 132.9 7.2 1.4 141.5 8.3 149.8 Net income attributable to Alliant Energy common shareowners 87.0 7.6 94.6 Three Months Ended June 30, 2018 Revenues $726.3 $68.6 $10.7 $805.6 $10.5 $816.1 Operating income 134.8 5.4 0.9 141.1 10.1 151.2 Net income attributable to Alliant Energy common shareowners 91.5 8.9 100.4 ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2019 Revenues $1,434.6 $281.0 $22.0 $1,737.6 $39.8 $1,777.4 Operating income 259.3 52.4 1.4 313.1 13.5 326.6 Net income attributable to Alliant Energy common shareowners 206.0 13.7 219.7 Six Months Ended June 30, 2018 Revenues $1,435.0 $254.2 $23.9 $1,713.1 $19.3 $1,732.4 Operating income 261.5 36.9 2.3 300.7 16.2 316.9 Net income attributable to Alliant Energy common shareowners 192.2 29.1 221.3 IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $392.3 $38.4 $10.5 $441.2 Operating income 68.9 4.2 1.4 74.5 Earnings available for common stock 45.0 Three Months Ended June 30, 2018 Revenues $422.1 $42.2 $10.5 $474.8 Operating income 73.5 2.5 1.7 77.7 Earnings available for common stock 51.7 Six Months Ended June 30, 2019 Revenues $812.1 $163.0 $21.2 $996.3 Operating income 115.7 30.5 1.8 148.0 Earnings available for common stock 98.3 Six Months Ended June 30, 2018 Revenues $827.8 $150.3 $22.5 $1,000.6 Operating income 131.0 19.4 2.9 153.3 Earnings available for common stock 98.4 WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $298.9 $26.8 $0.4 $326.1 Operating income 64.0 3.0 — 67.0 Earnings available for common stock 42.0 Three Months Ended June 30, 2018 Revenues $304.2 $26.4 $0.2 $330.8 Operating income (loss) 61.3 2.9 (0.8 ) 63.4 Earnings available for common stock 39.8 Six Months Ended June 30, 2019 Revenues $622.5 $118.0 $0.8 $741.3 Operating income (loss) 143.6 21.9 (0.4 ) 165.1 Earnings available for common stock 107.7 Six Months Ended June 30, 2018 Revenues $607.2 $103.9 $1.4 $712.5 Operating income (loss) 130.5 17.5 (0.6 ) 147.4 Earnings available for common stock 93.8
IPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations. ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended June 30, 2019 Revenues $691.2 $65.2 $10.9 $767.3 $22.9 $790.2 Operating income 132.9 7.2 1.4 141.5 8.3 149.8 Net income attributable to Alliant Energy common shareowners 87.0 7.6 94.6 Three Months Ended June 30, 2018 Revenues $726.3 $68.6 $10.7 $805.6 $10.5 $816.1 Operating income 134.8 5.4 0.9 141.1 10.1 151.2 Net income attributable to Alliant Energy common shareowners 91.5 8.9 100.4 ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2019 Revenues $1,434.6 $281.0 $22.0 $1,737.6 $39.8 $1,777.4 Operating income 259.3 52.4 1.4 313.1 13.5 326.6 Net income attributable to Alliant Energy common shareowners 206.0 13.7 219.7 Six Months Ended June 30, 2018 Revenues $1,435.0 $254.2 $23.9 $1,713.1 $19.3 $1,732.4 Operating income 261.5 36.9 2.3 300.7 16.2 316.9 Net income attributable to Alliant Energy common shareowners 192.2 29.1 221.3 IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $392.3 $38.4 $10.5 $441.2 Operating income 68.9 4.2 1.4 74.5 Earnings available for common stock 45.0 Three Months Ended June 30, 2018 Revenues $422.1 $42.2 $10.5 $474.8 Operating income 73.5 2.5 1.7 77.7 Earnings available for common stock 51.7 Six Months Ended June 30, 2019 Revenues $812.1 $163.0 $21.2 $996.3 Operating income 115.7 30.5 1.8 148.0 Earnings available for common stock 98.3 Six Months Ended June 30, 2018 Revenues $827.8 $150.3 $22.5 $1,000.6 Operating income 131.0 19.4 2.9 153.3 Earnings available for common stock 98.4 WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $298.9 $26.8 $0.4 $326.1 Operating income 64.0 3.0 — 67.0 Earnings available for common stock 42.0 Three Months Ended June 30, 2018 Revenues $304.2 $26.4 $0.2 $330.8 Operating income (loss) 61.3 2.9 (0.8 ) 63.4 Earnings available for common stock 39.8 Six Months Ended June 30, 2019 Revenues $622.5 $118.0 $0.8 $741.3 Operating income (loss) 143.6 21.9 (0.4 ) 165.1 Earnings available for common stock 107.7 Six Months Ended June 30, 2018 Revenues $607.2 $103.9 $1.4 $712.5 Operating income (loss) 130.5 17.5 (0.6 ) 147.4 Earnings available for common stock 93.8
WPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations. ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended June 30, 2019 Revenues $691.2 $65.2 $10.9 $767.3 $22.9 $790.2 Operating income 132.9 7.2 1.4 141.5 8.3 149.8 Net income attributable to Alliant Energy common shareowners 87.0 7.6 94.6 Three Months Ended June 30, 2018 Revenues $726.3 $68.6 $10.7 $805.6 $10.5 $816.1 Operating income 134.8 5.4 0.9 141.1 10.1 151.2 Net income attributable to Alliant Energy common shareowners 91.5 8.9 100.4 ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2019 Revenues $1,434.6 $281.0 $22.0 $1,737.6 $39.8 $1,777.4 Operating income 259.3 52.4 1.4 313.1 13.5 326.6 Net income attributable to Alliant Energy common shareowners 206.0 13.7 219.7 Six Months Ended June 30, 2018 Revenues $1,435.0 $254.2 $23.9 $1,713.1 $19.3 $1,732.4 Operating income 261.5 36.9 2.3 300.7 16.2 316.9 Net income attributable to Alliant Energy common shareowners 192.2 29.1 221.3 IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $392.3 $38.4 $10.5 $441.2 Operating income 68.9 4.2 1.4 74.5 Earnings available for common stock 45.0 Three Months Ended June 30, 2018 Revenues $422.1 $42.2 $10.5 $474.8 Operating income 73.5 2.5 1.7 77.7 Earnings available for common stock 51.7 Six Months Ended June 30, 2019 Revenues $812.1 $163.0 $21.2 $996.3 Operating income 115.7 30.5 1.8 148.0 Earnings available for common stock 98.3 Six Months Ended June 30, 2018 Revenues $827.8 $150.3 $22.5 $1,000.6 Operating income 131.0 19.4 2.9 153.3 Earnings available for common stock 98.4 WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $298.9 $26.8 $0.4 $326.1 Operating income 64.0 3.0 — 67.0 Earnings available for common stock 42.0 Three Months Ended June 30, 2018 Revenues $304.2 $26.4 $0.2 $330.8 Operating income (loss) 61.3 2.9 (0.8 ) 63.4 Earnings available for common stock 39.8 Six Months Ended June 30, 2019 Revenues $622.5 $118.0 $0.8 $741.3 Operating income (loss) 143.6 21.9 (0.4 ) 165.1 Earnings available for common stock 107.7 Six Months Ended June 30, 2018 Revenues $607.2 $103.9 $1.4 $712.5 Operating income (loss) 130.5 17.5 (0.6 ) 147.4 Earnings available for common stock 93.8

Related Parties

Related Parties	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Line Items]
Related Parties	RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 Corporate Services billings $47 $44 $90 $85 $35 $34 $68 $67 Sales credited 12 18 27 23 3 8 4 9 Purchases billed 74 80 158 173 29 20 59 37 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2019 December 31, 2018 June 30, 2019 December 31, 2018 Net payables to Corporate Services $108 $95 $72 $71 ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 ATC billings to WPL $27 $26 $54 $53 WPL billings to ATC 3 3 7 5 WPL owed ATC net amounts of $8 million as of June 30, 2019 and $8 million as of December 31, 2018 . WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 7 for discussion of WPL’s Sheboygan Falls Energy Facility lease.
IPL [Member]
Related Party Transactions [Line Items]
Related Parties	RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 Corporate Services billings $47 $44 $90 $85 $35 $34 $68 $67 Sales credited 12 18 27 23 3 8 4 9 Purchases billed 74 80 158 173 29 20 59 37 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2019 December 31, 2018 June 30, 2019 December 31, 2018 Net payables to Corporate Services $108 $95 $72 $71
WPL [Member]
Related Party Transactions [Line Items]
Related Parties	RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 Corporate Services billings $47 $44 $90 $85 $35 $34 $68 $67 Sales credited 12 18 27 23 3 8 4 9 Purchases billed 74 80 158 173 29 20 59 37 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2019 December 31, 2018 June 30, 2019 December 31, 2018 Net payables to Corporate Services $108 $95 $72 $71 ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 ATC billings to WPL $27 $26 $54 $53 WPL billings to ATC 3 3 7 5 WPL owed ATC net amounts of $8 million as of June 30, 2019 and $8 million as of December 31, 2018 . WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 7 for discussion of WPL’s Sheboygan Falls Energy Facility lease.

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policy)	6 Months Ended
	Jun. 30, 2019
General, Basis of Accounting	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 .
General, Use of Estimates	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, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019
General, Reclassification	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 cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d) .
Cash and Cash Equivalents	Cash and Cash Equivalents - At June 30, 2019 , Alliant Energy’s and WPL’s cash and cash equivalents included $161.8 million and $160.4 million of money market fund investments, with interest rates of 2.4% and 2.4% , respectively.
Leases	Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.
New Accounting Standards	New Accounting Standards - Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial statements. Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements. 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. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. 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. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases. Cash Flows Statements - On January 1, 2018, Alliant Energy and IPL adopted an accounting standard that 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 and IPL currently use a method of presentation that allocates cash flows between operating and investing activities based on daily transactional activity. For the six months ended June 30, 2018 , Alliant Energy and IPL initially utilized a method of presentation that allocated cash flows between operating and investing activities based on monthly transactional activity. For the six months ended June 30, 2018 , the change in method of presentation to daily transactional activity increased Alliant Energy’s and IPL’s operating cash flows by $339.4 million , and Alliant Energy’s and IPL’s operating cash flows increased to $274.4 million and $12.8 million , respectively.
IPL [Member]
General, Basis of Accounting	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 .
General, Use of Estimates	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, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019
General, Reclassification	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 cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d) .
Leases	Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.
New Accounting Standards	New Accounting Standards - Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial statements. Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements. 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. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. 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. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases. Cash Flows Statements - On January 1, 2018, Alliant Energy and IPL adopted an accounting standard that 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 and IPL currently use a method of presentation that allocates cash flows between operating and investing activities based on daily transactional activity. For the six months ended June 30, 2018 , Alliant Energy and IPL initially utilized a method of presentation that allocated cash flows between operating and investing activities based on monthly transactional activity. For the six months ended June 30, 2018 , the change in method of presentation to daily transactional activity increased Alliant Energy’s and IPL’s operating cash flows by $339.4 million , and Alliant Energy’s and IPL’s operating cash flows increased to $274.4 million and $12.8 million , respectively.
WPL [Member]
General, Basis of Accounting	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 .
General, Use of Estimates	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, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019
General, Reclassification	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 cash receipts on sold receivables in the cash flows statements as discussed in Note 1(d) .
Cash and Cash Equivalents	Cash and Cash Equivalents - At June 30, 2019 , Alliant Energy’s and WPL’s cash and cash equivalents included $161.8 million and $160.4 million of money market fund investments, with interest rates of 2.4% and 2.4% , respectively.
Leases	Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.
New Accounting Standards	New Accounting Standards - Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial statements. Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements. 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. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. 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. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2019
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $815.5 $820.6 $780.2 $783.1 $35.3 $37.5 Pension and OPEB costs 522.9 542.3 264.7 274.0 258.2 268.3 Asset retirement obligations 111.0 110.8 76.2 76.3 34.8 34.5 IPL’s DAEC PPA amendment 107.1 — 107.1 — — — EGUs retired early 102.8 111.6 51.7 55.4 51.1 56.2 Derivatives 30.6 28.0 13.4 15.1 17.2 12.9 Emission allowances 22.4 23.6 22.4 23.6 — — Other 94.6 100.4 48.8 51.5 45.8 48.9 $1,806.9 $1,737.3 $1,364.5 $1,279.0 $442.4 $458.3
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $853.8 $890.6 $365.6 $390.1 $488.2 $500.5 Cost of removal obligations 399.2 401.2 269.5 273.3 129.7 127.9 Electric transmission cost recovery 101.5 104.0 52.7 47.7 48.8 56.3 WPL’s earnings sharing mechanism 25.2 25.4 — — 25.2 25.4 Commodity cost recovery 22.7 16.8 11.9 11.9 10.8 4.9 Other 40.5 55.2 20.2 31.9 20.3 23.3 $1,442.9 $1,493.2 $719.9 $754.9 $723.0 $738.3
IPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $815.5 $820.6 $780.2 $783.1 $35.3 $37.5 Pension and OPEB costs 522.9 542.3 264.7 274.0 258.2 268.3 Asset retirement obligations 111.0 110.8 76.2 76.3 34.8 34.5 IPL’s DAEC PPA amendment 107.1 — 107.1 — — — EGUs retired early 102.8 111.6 51.7 55.4 51.1 56.2 Derivatives 30.6 28.0 13.4 15.1 17.2 12.9 Emission allowances 22.4 23.6 22.4 23.6 — — Other 94.6 100.4 48.8 51.5 45.8 48.9 $1,806.9 $1,737.3 $1,364.5 $1,279.0 $442.4 $458.3
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $853.8 $890.6 $365.6 $390.1 $488.2 $500.5 Cost of removal obligations 399.2 401.2 269.5 273.3 129.7 127.9 Electric transmission cost recovery 101.5 104.0 52.7 47.7 48.8 56.3 WPL’s earnings sharing mechanism 25.2 25.4 — — 25.2 25.4 Commodity cost recovery 22.7 16.8 11.9 11.9 10.8 4.9 Other 40.5 55.2 20.2 31.9 20.3 23.3 $1,442.9 $1,493.2 $719.9 $754.9 $723.0 $738.3
WPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $815.5 $820.6 $780.2 $783.1 $35.3 $37.5 Pension and OPEB costs 522.9 542.3 264.7 274.0 258.2 268.3 Asset retirement obligations 111.0 110.8 76.2 76.3 34.8 34.5 IPL’s DAEC PPA amendment 107.1 — 107.1 — — — EGUs retired early 102.8 111.6 51.7 55.4 51.1 56.2 Derivatives 30.6 28.0 13.4 15.1 17.2 12.9 Emission allowances 22.4 23.6 22.4 23.6 — — Other 94.6 100.4 48.8 51.5 45.8 48.9 $1,806.9 $1,737.3 $1,364.5 $1,279.0 $442.4 $458.3
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $853.8 $890.6 $365.6 $390.1 $488.2 $500.5 Cost of removal obligations 399.2 401.2 269.5 273.3 129.7 127.9 Electric transmission cost recovery 101.5 104.0 52.7 47.7 48.8 56.3 WPL’s earnings sharing mechanism 25.2 25.4 — — 25.2 25.4 Commodity cost recovery 22.7 16.8 11.9 11.9 10.8 4.9 Other 40.5 55.2 20.2 31.9 20.3 23.3 $1,442.9 $1,493.2 $719.9 $754.9 $723.0 $738.3

Receivables (Tables)

Receivables (Tables)	6 Months Ended
	Jun. 30, 2019
Receivables [Line Items]
Maximum And Average Outstanding Cash Proceeds	IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Maximum outstanding aggregate cash proceeds $25.0 $116.0 $108.0 $116.0 Average outstanding aggregate cash proceeds 2.6 52.3 41.6 56.7
Receivables Sold Under The Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2019 December 31, 2018 Customer accounts receivable $138.3 $140.1 Unbilled utility revenues 90.5 97.1 Other receivables 0.4 0.1 Receivables sold to third party 229.2 237.3 Less: cash proceeds 5.0 108.0 Deferred proceeds 224.2 129.3 Less: allowance for doubtful accounts 9.6 9.9 Fair value of deferred proceeds $214.6 $119.4
Additional Attributes Of Receivables Sold Under The Receivables Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Collections $487.7 $483.7 $1,043.5 $1,000.7 Write-offs, net of recoveries 2.6 1.9 8.1 8.0
IPL [Member]
Receivables [Line Items]
Maximum And Average Outstanding Cash Proceeds	IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Maximum outstanding aggregate cash proceeds $25.0 $116.0 $108.0 $116.0 Average outstanding aggregate cash proceeds 2.6 52.3 41.6 56.7
Receivables Sold Under The Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2019 December 31, 2018 Customer accounts receivable $138.3 $140.1 Unbilled utility revenues 90.5 97.1 Other receivables 0.4 0.1 Receivables sold to third party 229.2 237.3 Less: cash proceeds 5.0 108.0 Deferred proceeds 224.2 129.3 Less: allowance for doubtful accounts 9.6 9.9 Fair value of deferred proceeds $214.6 $119.4
Additional Attributes Of Receivables Sold Under The Receivables Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 Collections $487.7 $483.7 $1,043.5 $1,000.7 Write-offs, net of recoveries 2.6 1.9 8.1 8.0

Investments and Acquisitions (T

Investments and Acquisitions (Tables)	6 Months Ended
	Jun. 30, 2019
Schedule of Investments [Line Items]
Unconsolidated Equity Investments	Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and six months ended June 30 was as follows (in millions): Three Months Six Months 2019 2018 2019 2018 ATC Holdings ($10.0 ) ($7.8 ) ($19.5 ) ($16.5 ) Non-utility wind farm in Oklahoma (1.3 ) (2.5 ) (2.4 ) (14.6 ) Other (1.4 ) (0.2 ) (1.7 ) (0.7 ) ($12.7 ) ($10.5 ) ($23.6 ) ($31.8 )

Common Equity (Tables)

Common Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Schedule of Capitalization, Equity [Line Items]
Common Share Activity	A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2019 236,063,279 Equity forward agreements 1,090,300 Shareowner Direct Plan 268,755 Equity-based compensation plans 101,478 Other (2,738 ) Shares outstanding, June 30, 2019 237,521,074
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $2.4 $2,100.0 $2,587.3 $2.4 ($9.7 ) $200.0 $4,882.4 Net income attributable to Alliant Energy common shareowners 94.6 94.6 Common stock dividends ($0.355 per share) (84.1 ) (84.1 ) Shareowner Direct Plan issuances 6.0 6.0 Equity-based compensation plans and other 2.4 (0.3 ) 2.1 Other comprehensive loss, net of tax (1.4 ) (1.4 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Three Months Ended June 30, 2018 Beginning balance, April 1 $2.3 $1,851.4 $2,389.4 ($0.5 ) ($11.1 ) $200.0 $4,431.5 Net income attributable to Alliant Energy common shareowners 100.4 100.4 Common stock dividends ($0.335 per share) (77.3 ) (77.3 ) At-the-market offering program and Shareowner Direct Plan issuances 93.8 93.8 Equity-based compensation plans and other 2.0 (0.3 ) 1.7 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $2.4 $2,045.5 $2,545.9 $1.7 ($9.8 ) $200.0 $4,785.7 Net income attributable to Alliant Energy common shareowners 219.7 219.7 Common stock dividends ($0.71 per share) (167.8 ) (167.8 ) Equity forward settlements and Shareowner Direct Plan issuances 60.6 60.6 Equity-based compensation plans and other 2.3 (0.2 ) 2.1 Other comprehensive loss, net of tax (0.7 ) (0.7 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Six Months Ended June 30, 2018 Beginning balance, January 1 $2.3 $1,845.5 $2,346.0 ($0.5 ) ($11.1 ) $200.0 $4,382.2 Net income attributable to Alliant Energy common shareowners 221.3 221.3 Common stock dividends ($0.67 per share) (154.8 ) (154.8 ) At-the-market offering program and Shareowner Direct Plan issuances 100.1 100.1 Equity-based compensation plans and other 1.6 (0.3 ) 1.3 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $33.4 $2,322.8 $785.8 $200.0 $3,342.0 Earnings available for common stock 45.0 45.0 Common stock dividends (41.9 ) (41.9 ) Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Three Months Ended June 30, 2018 Beginning balance, April 1 $33.4 $1,797.8 $683.3 $200.0 $2,714.5 Earnings available for common stock 51.7 51.7 Common stock dividends (42.1 ) (42.1 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $33.4 $2,222.8 $774.5 $200.0 $3,230.7 Earnings available for common stock 98.3 98.3 Common stock dividends (83.9 ) (83.9 ) Capital contributions from parent 100.0 100.0 Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Six Months Ended June 30, 2018 Beginning balance, January 1 $33.4 $1,797.8 $678.5 $200.0 $2,709.7 Earnings available for common stock 98.4 98.4 Common stock dividends (84.0 ) (84.0 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $66.2 $1,309.0 $804.0 $2,179.2 Earnings available for common stock 42.0 42.0 Common stock dividends (36.0 ) (36.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Three Months Ended June 30, 2018 Beginning balance, April 1 $66.2 $1,109.0 $725.3 $1,900.5 Earnings available for common stock 39.8 39.8 Common stock dividends (35.1 ) (35.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $66.2 $1,309.0 $774.3 $2,149.5 Earnings available for common stock 107.7 107.7 Common stock dividends (72.0 ) (72.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Six Months Ended June 30, 2018 Beginning balance, January 1 $66.2 $1,109.0 $706.3 $1,881.5 Earnings available for common stock 93.8 93.8 Common stock dividends (70.1 ) (70.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2
IPL [Member]
Schedule of Capitalization, Equity [Line Items]
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $2.4 $2,100.0 $2,587.3 $2.4 ($9.7 ) $200.0 $4,882.4 Net income attributable to Alliant Energy common shareowners 94.6 94.6 Common stock dividends ($0.355 per share) (84.1 ) (84.1 ) Shareowner Direct Plan issuances 6.0 6.0 Equity-based compensation plans and other 2.4 (0.3 ) 2.1 Other comprehensive loss, net of tax (1.4 ) (1.4 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Three Months Ended June 30, 2018 Beginning balance, April 1 $2.3 $1,851.4 $2,389.4 ($0.5 ) ($11.1 ) $200.0 $4,431.5 Net income attributable to Alliant Energy common shareowners 100.4 100.4 Common stock dividends ($0.335 per share) (77.3 ) (77.3 ) At-the-market offering program and Shareowner Direct Plan issuances 93.8 93.8 Equity-based compensation plans and other 2.0 (0.3 ) 1.7 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $2.4 $2,045.5 $2,545.9 $1.7 ($9.8 ) $200.0 $4,785.7 Net income attributable to Alliant Energy common shareowners 219.7 219.7 Common stock dividends ($0.71 per share) (167.8 ) (167.8 ) Equity forward settlements and Shareowner Direct Plan issuances 60.6 60.6 Equity-based compensation plans and other 2.3 (0.2 ) 2.1 Other comprehensive loss, net of tax (0.7 ) (0.7 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Six Months Ended June 30, 2018 Beginning balance, January 1 $2.3 $1,845.5 $2,346.0 ($0.5 ) ($11.1 ) $200.0 $4,382.2 Net income attributable to Alliant Energy common shareowners 221.3 221.3 Common stock dividends ($0.67 per share) (154.8 ) (154.8 ) At-the-market offering program and Shareowner Direct Plan issuances 100.1 100.1 Equity-based compensation plans and other 1.6 (0.3 ) 1.3 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $33.4 $2,322.8 $785.8 $200.0 $3,342.0 Earnings available for common stock 45.0 45.0 Common stock dividends (41.9 ) (41.9 ) Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Three Months Ended June 30, 2018 Beginning balance, April 1 $33.4 $1,797.8 $683.3 $200.0 $2,714.5 Earnings available for common stock 51.7 51.7 Common stock dividends (42.1 ) (42.1 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $33.4 $2,222.8 $774.5 $200.0 $3,230.7 Earnings available for common stock 98.3 98.3 Common stock dividends (83.9 ) (83.9 ) Capital contributions from parent 100.0 100.0 Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Six Months Ended June 30, 2018 Beginning balance, January 1 $33.4 $1,797.8 $678.5 $200.0 $2,709.7 Earnings available for common stock 98.4 98.4 Common stock dividends (84.0 ) (84.0 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $66.2 $1,309.0 $804.0 $2,179.2 Earnings available for common stock 42.0 42.0 Common stock dividends (36.0 ) (36.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Three Months Ended June 30, 2018 Beginning balance, April 1 $66.2 $1,109.0 $725.3 $1,900.5 Earnings available for common stock 39.8 39.8 Common stock dividends (35.1 ) (35.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $66.2 $1,309.0 $774.3 $2,149.5 Earnings available for common stock 107.7 107.7 Common stock dividends (72.0 ) (72.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Six Months Ended June 30, 2018 Beginning balance, January 1 $66.2 $1,109.0 $706.3 $1,881.5 Earnings available for common stock 93.8 93.8 Common stock dividends (70.1 ) (70.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2
WPL [Member]
Schedule of Capitalization, Equity [Line Items]
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $2.4 $2,100.0 $2,587.3 $2.4 ($9.7 ) $200.0 $4,882.4 Net income attributable to Alliant Energy common shareowners 94.6 94.6 Common stock dividends ($0.355 per share) (84.1 ) (84.1 ) Shareowner Direct Plan issuances 6.0 6.0 Equity-based compensation plans and other 2.4 (0.3 ) 2.1 Other comprehensive loss, net of tax (1.4 ) (1.4 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Three Months Ended June 30, 2018 Beginning balance, April 1 $2.3 $1,851.4 $2,389.4 ($0.5 ) ($11.1 ) $200.0 $4,431.5 Net income attributable to Alliant Energy common shareowners 100.4 100.4 Common stock dividends ($0.335 per share) (77.3 ) (77.3 ) At-the-market offering program and Shareowner Direct Plan issuances 93.8 93.8 Equity-based compensation plans and other 2.0 (0.3 ) 1.7 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Income (Loss) Trust of IPL Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $2.4 $2,045.5 $2,545.9 $1.7 ($9.8 ) $200.0 $4,785.7 Net income attributable to Alliant Energy common shareowners 219.7 219.7 Common stock dividends ($0.71 per share) (167.8 ) (167.8 ) Equity forward settlements and Shareowner Direct Plan issuances 60.6 60.6 Equity-based compensation plans and other 2.3 (0.2 ) 2.1 Other comprehensive loss, net of tax (0.7 ) (0.7 ) Ending balance, June 30 $2.4 $2,108.4 $2,597.8 $1.0 ($10.0 ) $200.0 $4,899.6 Six Months Ended June 30, 2018 Beginning balance, January 1 $2.3 $1,845.5 $2,346.0 ($0.5 ) ($11.1 ) $200.0 $4,382.2 Net income attributable to Alliant Energy common shareowners 221.3 221.3 Common stock dividends ($0.67 per share) (154.8 ) (154.8 ) At-the-market offering program and Shareowner Direct Plan issuances 100.1 100.1 Equity-based compensation plans and other 1.6 (0.3 ) 1.3 Other comprehensive income, net of tax 0.6 0.6 Ending balance, June 30 $2.3 $1,947.2 $2,412.5 $0.1 ($11.4 ) $200.0 $4,550.7 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $33.4 $2,322.8 $785.8 $200.0 $3,342.0 Earnings available for common stock 45.0 45.0 Common stock dividends (41.9 ) (41.9 ) Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Three Months Ended June 30, 2018 Beginning balance, April 1 $33.4 $1,797.8 $683.3 $200.0 $2,714.5 Earnings available for common stock 51.7 51.7 Common stock dividends (42.1 ) (42.1 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $33.4 $2,222.8 $774.5 $200.0 $3,230.7 Earnings available for common stock 98.3 98.3 Common stock dividends (83.9 ) (83.9 ) Capital contributions from parent 100.0 100.0 Ending balance, June 30 $33.4 $2,322.8 $788.9 $200.0 $3,345.1 Six Months Ended June 30, 2018 Beginning balance, January 1 $33.4 $1,797.8 $678.5 $200.0 $2,709.7 Earnings available for common stock 98.4 98.4 Common stock dividends (84.0 ) (84.0 ) Capital contributions from parent 130.0 130.0 Ending balance, June 30 $33.4 $1,927.8 $692.9 $200.0 $2,854.1 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2019 Beginning balance, April 1 $66.2 $1,309.0 $804.0 $2,179.2 Earnings available for common stock 42.0 42.0 Common stock dividends (36.0 ) (36.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Three Months Ended June 30, 2018 Beginning balance, April 1 $66.2 $1,109.0 $725.3 $1,900.5 Earnings available for common stock 39.8 39.8 Common stock dividends (35.1 ) (35.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2019 Beginning balance, January 1 $66.2 $1,309.0 $774.3 $2,149.5 Earnings available for common stock 107.7 107.7 Common stock dividends (72.0 ) (72.0 ) Ending balance, June 30 $66.2 $1,309.0 $810.0 $2,185.2 Six Months Ended June 30, 2018 Beginning balance, January 1 $66.2 $1,109.0 $706.3 $1,881.5 Earnings available for common stock 93.8 93.8 Common stock dividends (70.1 ) (70.1 ) Capital contributions from parent 150.0 150.0 Ending balance, June 30 $66.2 $1,259.0 $730.0 $2,055.2

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2019
Short-term Debt [Line Items]
Other Short-Term Borrowings	Information regarding commercial paper classified as short-term debt was as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Commercial paper outstanding $390.5 $— $— Commercial paper weighted average interest rates 2.6% N/A N/A Available credit facility capacity $609.5 $250.0 $300.0 Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Maximum amount outstanding (based on daily outstanding balances) $590.2 $446.5 $— $31.4 $193.3 $109.4 Average amount outstanding (based on daily outstanding balances) $531.7 $234.5 $— $5.1 $141.6 $45.2 Weighted average interest rates 2.7% 2.2% N/A 2.3% 2.5% 1.8% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $600.6 $446.5 $50.4 $31.4 $195.1 $109.4 Average amount outstanding (based on daily outstanding balances) $515.4 $272.1 $0.3 $2.6 $139.8 $28.4 Weighted average interest rates 2.7% 2.0% 2.8% 2.3% 2.5% 1.8%
IPL [Member]
Short-term Debt [Line Items]
Other Short-Term Borrowings	Information regarding commercial paper classified as short-term debt was as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Commercial paper outstanding $390.5 $— $— Commercial paper weighted average interest rates 2.6% N/A N/A Available credit facility capacity $609.5 $250.0 $300.0 Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Maximum amount outstanding (based on daily outstanding balances) $590.2 $446.5 $— $31.4 $193.3 $109.4 Average amount outstanding (based on daily outstanding balances) $531.7 $234.5 $— $5.1 $141.6 $45.2 Weighted average interest rates 2.7% 2.2% N/A 2.3% 2.5% 1.8% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $600.6 $446.5 $50.4 $31.4 $195.1 $109.4 Average amount outstanding (based on daily outstanding balances) $515.4 $272.1 $0.3 $2.6 $139.8 $28.4 Weighted average interest rates 2.7% 2.0% 2.8% 2.3% 2.5% 1.8%
WPL [Member]
Short-term Debt [Line Items]
Other Short-Term Borrowings	Information regarding commercial paper classified as short-term debt was as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Commercial paper outstanding $390.5 $— $— Commercial paper weighted average interest rates 2.6% N/A N/A Available credit facility capacity $609.5 $250.0 $300.0 Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Maximum amount outstanding (based on daily outstanding balances) $590.2 $446.5 $— $31.4 $193.3 $109.4 Average amount outstanding (based on daily outstanding balances) $531.7 $234.5 $— $5.1 $141.6 $45.2 Weighted average interest rates 2.7% 2.2% N/A 2.3% 2.5% 1.8% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $600.6 $446.5 $50.4 $31.4 $195.1 $109.4 Average amount outstanding (based on daily outstanding balances) $515.4 $272.1 $0.3 $2.6 $139.8 $28.4 Weighted average interest rates 2.7% 2.0% 2.8% 2.3% 2.5% 1.8%

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Line Items]
Schedule of Lease Details	Operating lease details are as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $—
Schedule of Operating Lease Liability Maturities	As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64
Schedule of Future Minimum Payments for Operating Leases	As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68
IPL [Member]
Leases [Line Items]
Schedule of Lease Details	Operating lease details are as follows (dollars in millions): June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $—
Schedule of Operating Lease Liability Maturities	As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64
Schedule of Future Minimum Payments for Operating Leases	As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68
WPL [Member]
Leases [Line Items]
Schedule of Lease Details	WPL’s finance lease details are as follows (dollars in millions): June 30, 2019 Property, plant and equipment, net $35 Other current liabilities $8 Finance lease obligations - Sheboygan Falls Energy Facility 56 Total finance lease liabilities $64 Remaining lease term 6 years Discount rate 11 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Depreciation expense $2 $3 Interest expense 2 4 Total finance lease expense $4 $7 June 30, 2019 Alliant Energy IPL WPL Property, plant and equipment, net $17 $10 $7 Other current liabilities $2 $1 $1 Other liabilities 15 9 6 Total operating lease liabilities $17 $10 $7 Weighted average remaining lease term 11 years 13 years 10 years Weighted average discount rate 4 % 4 % 4 % Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Alliant Energy IPL WPL Alliant Energy IPL WPL Operating lease cost $— $— $— $1 $— $—
Schedule of Operating Lease Liability Maturities	As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64
Schedule of Finance Lease Liability Maturities	As of June 30, 2019 , expected maturities of lease liabilities were as follows (in millions): Remainder of 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $13 $23 $6 $17 IPL 1 1 1 1 1 9 14 4 10 WPL 1 1 1 1 1 4 9 2 7 WPL’s Finance Lease: Sheboygan Falls Energy Facility 7 15 15 15 15 20 87 23 64
Schedule of Future Minimum Payments for Operating Leases	As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68
Schedule of Future Minimum Payments for Capital Leases	As of December 31, 2018 , future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions): 2019 2020 2021 2022 2023 Thereafter Total Less: amount representing interest Present value of minimum capital lease payments Operating Leases: Alliant Energy $5 $5 $3 $3 $2 $12 $30 IPL 3 2 2 2 2 12 23 WPL 2 3 1 — — — 6 WPL’s Capital Lease: Sheboygan Falls Energy Facility $15 $15 $15 $15 $15 $19 $94 $26 $68

Revenues (Tables)

Revenues (Tables)	6 Months Ended
	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $233.3 $248.3 $125.9 $139.3 $107.4 $109.0 Retail - commercial 171.3 172.3 111.4 114.2 59.9 58.1 Retail - industrial 214.2 225.4 118.4 128.8 95.8 96.6 Wholesale 41.0 43.1 14.6 13.9 26.4 29.2 Bulk power and other 31.4 37.2 22.0 25.9 9.4 11.3 Total Electric Utility 691.2 726.3 392.3 422.1 298.9 304.2 Gas Utility: Retail - residential 35.2 37.7 20.0 22.8 15.2 14.9 Retail - commercial 16.1 19.3 8.8 11.8 7.3 7.5 Retail - industrial 2.0 2.6 1.6 1.4 0.4 1.2 Transportation/other 11.9 9.0 8.0 6.2 3.9 2.8 Total Gas Utility 65.2 68.6 38.4 42.2 26.8 26.4 Other Utility: Steam 9.2 8.4 9.2 8.4 — — Other utility 1.7 2.3 1.3 2.1 0.4 0.2 Total Other Utility 10.9 10.7 10.5 10.5 0.4 0.2 Non-Utility and Other: Transportation and other 22.9 10.5 — — — — Total Non-Utility and Other 22.9 10.5 — — — — Total revenues $790.2 $816.1 $441.2 $474.8 $326.1 $330.8 Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $508.0 $507.7 $273.4 $281.5 $234.6 $226.2 Retail - commercial 352.4 346.3 228.0 225.8 124.4 120.5 Retail - industrial 422.9 427.3 234.5 243.6 188.4 183.7 Wholesale 87.5 96.9 31.5 38.2 56.0 58.7 Bulk power and other 63.8 56.8 44.7 38.7 19.1 18.1 Total Electric Utility 1,434.6 1,435.0 812.1 827.8 622.5 607.2 Gas Utility: Retail - residential 167.0 148.3 97.9 88.3 69.1 60.0 Retail - commercial 79.7 76.3 43.6 43.4 36.1 32.9 Retail - industrial 7.4 8.4 4.8 4.1 2.6 4.3 Transportation/other 26.9 21.2 16.7 14.5 10.2 6.7 Total Gas Utility 281.0 254.2 163.0 150.3 118.0 103.9 Other Utility: Steam 17.6 17.8 17.6 17.8 — — Other utility 4.4 6.1 3.6 4.7 0.8 1.4 Total Other Utility 22.0 23.9 21.2 22.5 0.8 1.4 Non-Utility and Other: Transportation and other 39.8 19.3 — — — — Total Non-Utility and Other 39.8 19.3 — — — — Total revenues $1,777.4 $1,732.4 $996.3 $1,000.6 $741.3 $712.5
IPL [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $233.3 $248.3 $125.9 $139.3 $107.4 $109.0 Retail - commercial 171.3 172.3 111.4 114.2 59.9 58.1 Retail - industrial 214.2 225.4 118.4 128.8 95.8 96.6 Wholesale 41.0 43.1 14.6 13.9 26.4 29.2 Bulk power and other 31.4 37.2 22.0 25.9 9.4 11.3 Total Electric Utility 691.2 726.3 392.3 422.1 298.9 304.2 Gas Utility: Retail - residential 35.2 37.7 20.0 22.8 15.2 14.9 Retail - commercial 16.1 19.3 8.8 11.8 7.3 7.5 Retail - industrial 2.0 2.6 1.6 1.4 0.4 1.2 Transportation/other 11.9 9.0 8.0 6.2 3.9 2.8 Total Gas Utility 65.2 68.6 38.4 42.2 26.8 26.4 Other Utility: Steam 9.2 8.4 9.2 8.4 — — Other utility 1.7 2.3 1.3 2.1 0.4 0.2 Total Other Utility 10.9 10.7 10.5 10.5 0.4 0.2 Non-Utility and Other: Transportation and other 22.9 10.5 — — — — Total Non-Utility and Other 22.9 10.5 — — — — Total revenues $790.2 $816.1 $441.2 $474.8 $326.1 $330.8 Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $508.0 $507.7 $273.4 $281.5 $234.6 $226.2 Retail - commercial 352.4 346.3 228.0 225.8 124.4 120.5 Retail - industrial 422.9 427.3 234.5 243.6 188.4 183.7 Wholesale 87.5 96.9 31.5 38.2 56.0 58.7 Bulk power and other 63.8 56.8 44.7 38.7 19.1 18.1 Total Electric Utility 1,434.6 1,435.0 812.1 827.8 622.5 607.2 Gas Utility: Retail - residential 167.0 148.3 97.9 88.3 69.1 60.0 Retail - commercial 79.7 76.3 43.6 43.4 36.1 32.9 Retail - industrial 7.4 8.4 4.8 4.1 2.6 4.3 Transportation/other 26.9 21.2 16.7 14.5 10.2 6.7 Total Gas Utility 281.0 254.2 163.0 150.3 118.0 103.9 Other Utility: Steam 17.6 17.8 17.6 17.8 — — Other utility 4.4 6.1 3.6 4.7 0.8 1.4 Total Other Utility 22.0 23.9 21.2 22.5 0.8 1.4 Non-Utility and Other: Transportation and other 39.8 19.3 — — — — Total Non-Utility and Other 39.8 19.3 — — — — Total revenues $1,777.4 $1,732.4 $996.3 $1,000.6 $741.3 $712.5
WPL [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $233.3 $248.3 $125.9 $139.3 $107.4 $109.0 Retail - commercial 171.3 172.3 111.4 114.2 59.9 58.1 Retail - industrial 214.2 225.4 118.4 128.8 95.8 96.6 Wholesale 41.0 43.1 14.6 13.9 26.4 29.2 Bulk power and other 31.4 37.2 22.0 25.9 9.4 11.3 Total Electric Utility 691.2 726.3 392.3 422.1 298.9 304.2 Gas Utility: Retail - residential 35.2 37.7 20.0 22.8 15.2 14.9 Retail - commercial 16.1 19.3 8.8 11.8 7.3 7.5 Retail - industrial 2.0 2.6 1.6 1.4 0.4 1.2 Transportation/other 11.9 9.0 8.0 6.2 3.9 2.8 Total Gas Utility 65.2 68.6 38.4 42.2 26.8 26.4 Other Utility: Steam 9.2 8.4 9.2 8.4 — — Other utility 1.7 2.3 1.3 2.1 0.4 0.2 Total Other Utility 10.9 10.7 10.5 10.5 0.4 0.2 Non-Utility and Other: Transportation and other 22.9 10.5 — — — — Total Non-Utility and Other 22.9 10.5 — — — — Total revenues $790.2 $816.1 $441.2 $474.8 $326.1 $330.8 Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Electric Utility: Retail - residential $508.0 $507.7 $273.4 $281.5 $234.6 $226.2 Retail - commercial 352.4 346.3 228.0 225.8 124.4 120.5 Retail - industrial 422.9 427.3 234.5 243.6 188.4 183.7 Wholesale 87.5 96.9 31.5 38.2 56.0 58.7 Bulk power and other 63.8 56.8 44.7 38.7 19.1 18.1 Total Electric Utility 1,434.6 1,435.0 812.1 827.8 622.5 607.2 Gas Utility: Retail - residential 167.0 148.3 97.9 88.3 69.1 60.0 Retail - commercial 79.7 76.3 43.6 43.4 36.1 32.9 Retail - industrial 7.4 8.4 4.8 4.1 2.6 4.3 Transportation/other 26.9 21.2 16.7 14.5 10.2 6.7 Total Gas Utility 281.0 254.2 163.0 150.3 118.0 103.9 Other Utility: Steam 17.6 17.8 17.6 17.8 — — Other utility 4.4 6.1 3.6 4.7 0.8 1.4 Total Other Utility 22.0 23.9 21.2 22.5 0.8 1.4 Non-Utility and Other: Transportation and other 39.8 19.3 — — — — Total Non-Utility and Other 39.8 19.3 — — — — Total revenues $1,777.4 $1,732.4 $996.3 $1,000.6 $741.3 $712.5

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2019
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes. Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.5 6.5 8.3 7.0 6.2 6.2 Production tax credits (8.5 ) (5.4 ) (13.2 ) (5.3 ) (4.2 ) (6.8 ) Effect of rate-making on property-related differences (6.2 ) (6.7 ) (10.1 ) (11.5 ) (2.7 ) (2.7 ) Amortization of excess deferred taxes (1.3 ) (0.4 ) (0.4 ) — (2.3 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.1 ) (1.4 ) (4.3 ) — — Other items, net (1.5 ) (1.2 ) (0.4 ) (2.8 ) (2.5 ) (4.1 ) Overall income tax rate 10.3 % 11.7 % 3.8 % 4.1 % 15.5 % 13.5 % Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.2 7.1 8.1 7.7 6.2 6.2 Production tax credits (8.9 ) (5.5 ) (13.6 ) (5.3 ) (4.6 ) (6.7 ) Effect of rate-making on property-related differences (6.0 ) (7.2 ) (9.6 ) (12.4 ) (2.4 ) (2.5 ) Amortization of excess deferred taxes (1.1 ) (0.4 ) (0.3 ) — (1.8 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.2 ) (1.4 ) (4.5 ) — — Other items, net (1.0 ) (1.0 ) (0.5 ) (1.5 ) (1.2 ) (1.9 ) Overall income tax rate 10.5 % 11.8 % 3.7 % 5.0 % 17.2 % 16.0 %
Summary Of Tax Credit Carryforwards	At June 30, 2019 , carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2031-2037 $760 $550 $122 State net operating losses 2019-2039 764 13 2 Federal tax credits 2022-2039 325 152 154
IPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes. Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.5 6.5 8.3 7.0 6.2 6.2 Production tax credits (8.5 ) (5.4 ) (13.2 ) (5.3 ) (4.2 ) (6.8 ) Effect of rate-making on property-related differences (6.2 ) (6.7 ) (10.1 ) (11.5 ) (2.7 ) (2.7 ) Amortization of excess deferred taxes (1.3 ) (0.4 ) (0.4 ) — (2.3 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.1 ) (1.4 ) (4.3 ) — — Other items, net (1.5 ) (1.2 ) (0.4 ) (2.8 ) (2.5 ) (4.1 ) Overall income tax rate 10.3 % 11.7 % 3.8 % 4.1 % 15.5 % 13.5 % Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.2 7.1 8.1 7.7 6.2 6.2 Production tax credits (8.9 ) (5.5 ) (13.6 ) (5.3 ) (4.6 ) (6.7 ) Effect of rate-making on property-related differences (6.0 ) (7.2 ) (9.6 ) (12.4 ) (2.4 ) (2.5 ) Amortization of excess deferred taxes (1.1 ) (0.4 ) (0.3 ) — (1.8 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.2 ) (1.4 ) (4.5 ) — — Other items, net (1.0 ) (1.0 ) (0.5 ) (1.5 ) (1.2 ) (1.9 ) Overall income tax rate 10.5 % 11.8 % 3.7 % 5.0 % 17.2 % 16.0 %
Summary Of Tax Credit Carryforwards	At June 30, 2019 , carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2031-2037 $760 $550 $122 State net operating losses 2019-2039 764 13 2 Federal tax credits 2022-2039 325 152 154
WPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes. Alliant Energy IPL WPL Three Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.5 6.5 8.3 7.0 6.2 6.2 Production tax credits (8.5 ) (5.4 ) (13.2 ) (5.3 ) (4.2 ) (6.8 ) Effect of rate-making on property-related differences (6.2 ) (6.7 ) (10.1 ) (11.5 ) (2.7 ) (2.7 ) Amortization of excess deferred taxes (1.3 ) (0.4 ) (0.4 ) — (2.3 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.1 ) (1.4 ) (4.3 ) — — Other items, net (1.5 ) (1.2 ) (0.4 ) (2.8 ) (2.5 ) (4.1 ) Overall income tax rate 10.3 % 11.7 % 3.8 % 4.1 % 15.5 % 13.5 % Alliant Energy IPL WPL Six Months Ended June 30 2019 2018 2019 2018 2019 2018 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefits 7.2 7.1 8.1 7.7 6.2 6.2 Production tax credits (8.9 ) (5.5 ) (13.6 ) (5.3 ) (4.6 ) (6.7 ) Effect of rate-making on property-related differences (6.0 ) (7.2 ) (9.6 ) (12.4 ) (2.4 ) (2.5 ) Amortization of excess deferred taxes (1.1 ) (0.4 ) (0.3 ) — (1.8 ) (0.1 ) IPL’s tax benefit riders (0.7 ) (2.2 ) (1.4 ) (4.5 ) — — Other items, net (1.0 ) (1.0 ) (0.5 ) (1.5 ) (1.2 ) (1.9 ) Overall income tax rate 10.5 % 11.8 % 3.7 % 5.0 % 17.2 % 16.0 %
Summary Of Tax Credit Carryforwards	At June 30, 2019 , carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2031-2037 $760 $550 $122 State net operating losses 2019-2039 764 13 2 Federal tax credits 2022-2039 325 152 154

Benefit Plans (Tables)

Benefit Plans (Tables)	6 Months Ended
	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Pension And Other Postretirement Benefits Plans	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and six months ended June 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months Alliant Energy 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $2.4 $3.0 $4.8 $6.0 $0.9 $1.0 $1.7 $2.1 Interest cost 12.4 11.7 24.9 23.4 2.1 1.9 4.2 3.8 Expected return on plan assets (15.0 ) (17.5 ) (30.0 ) (34.9 ) (1.3 ) (1.5 ) (2.5 ) (3.0 ) Amortization of prior service credit (0.1 ) (0.1 ) (0.3 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 9.1 8.8 18.2 17.6 0.8 0.9 1.6 1.7 $8.8 $5.9 $17.6 $11.8 $2.4 $2.2 $4.9 $4.5 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $1.5 $1.9 $3.0 $3.7 $0.4 $0.5 $0.7 $0.9 Interest cost 5.7 5.4 11.4 10.7 0.9 0.8 1.7 1.6 Expected return on plan assets (7.1 ) (8.2 ) (14.1 ) (16.3 ) (0.9 ) (1.1 ) (1.8 ) (2.2 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) — — — — Amortization of actuarial loss 4.0 3.8 7.9 7.5 0.3 0.3 0.7 0.6 $4.1 $2.8 $8.1 $5.5 $0.7 $0.5 $1.3 $0.9 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $0.8 $1.1 $1.7 $2.2 $0.3 $0.4 $0.6 $0.8 Interest cost 5.4 5.1 10.8 10.1 0.9 0.7 1.7 1.5 Expected return on plan assets (6.6 ) (7.6 ) (13.1 ) (15.2 ) (0.2 ) (0.1 ) (0.3 ) (0.3 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 4.4 4.3 8.8 8.6 0.4 0.5 0.8 1.0 $4.0 $2.8 $8.1 $5.6 $1.3 $1.4 $2.7 $2.9
Recognized Compensation Expense And Income Tax Benefits	A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 Compensation expense $3.4 $5.1 $8.1 $8.4 $1.9 $2.8 $4.5 $4.6 $1.4 $2.1 $3.2 $3.4 Income tax benefits 1.0 1.5 2.3 2.4 0.5 0.9 1.3 1.4 0.4 0.5 0.9 0.9
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Pension And Other Postretirement Benefits Plans	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and six months ended June 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months Alliant Energy 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $2.4 $3.0 $4.8 $6.0 $0.9 $1.0 $1.7 $2.1 Interest cost 12.4 11.7 24.9 23.4 2.1 1.9 4.2 3.8 Expected return on plan assets (15.0 ) (17.5 ) (30.0 ) (34.9 ) (1.3 ) (1.5 ) (2.5 ) (3.0 ) Amortization of prior service credit (0.1 ) (0.1 ) (0.3 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 9.1 8.8 18.2 17.6 0.8 0.9 1.6 1.7 $8.8 $5.9 $17.6 $11.8 $2.4 $2.2 $4.9 $4.5 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $1.5 $1.9 $3.0 $3.7 $0.4 $0.5 $0.7 $0.9 Interest cost 5.7 5.4 11.4 10.7 0.9 0.8 1.7 1.6 Expected return on plan assets (7.1 ) (8.2 ) (14.1 ) (16.3 ) (0.9 ) (1.1 ) (1.8 ) (2.2 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) — — — — Amortization of actuarial loss 4.0 3.8 7.9 7.5 0.3 0.3 0.7 0.6 $4.1 $2.8 $8.1 $5.5 $0.7 $0.5 $1.3 $0.9 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $0.8 $1.1 $1.7 $2.2 $0.3 $0.4 $0.6 $0.8 Interest cost 5.4 5.1 10.8 10.1 0.9 0.7 1.7 1.5 Expected return on plan assets (6.6 ) (7.6 ) (13.1 ) (15.2 ) (0.2 ) (0.1 ) (0.3 ) (0.3 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 4.4 4.3 8.8 8.6 0.4 0.5 0.8 1.0 $4.0 $2.8 $8.1 $5.6 $1.3 $1.4 $2.7 $2.9
Recognized Compensation Expense And Income Tax Benefits	A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 Compensation expense $3.4 $5.1 $8.1 $8.4 $1.9 $2.8 $4.5 $4.6 $1.4 $2.1 $3.2 $3.4 Income tax benefits 1.0 1.5 2.3 2.4 0.5 0.9 1.3 1.4 0.4 0.5 0.9 0.9
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Pension And Other Postretirement Benefits Plans	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and six months ended June 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months Alliant Energy 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $2.4 $3.0 $4.8 $6.0 $0.9 $1.0 $1.7 $2.1 Interest cost 12.4 11.7 24.9 23.4 2.1 1.9 4.2 3.8 Expected return on plan assets (15.0 ) (17.5 ) (30.0 ) (34.9 ) (1.3 ) (1.5 ) (2.5 ) (3.0 ) Amortization of prior service credit (0.1 ) (0.1 ) (0.3 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 9.1 8.8 18.2 17.6 0.8 0.9 1.6 1.7 $8.8 $5.9 $17.6 $11.8 $2.4 $2.2 $4.9 $4.5 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $1.5 $1.9 $3.0 $3.7 $0.4 $0.5 $0.7 $0.9 Interest cost 5.7 5.4 11.4 10.7 0.9 0.8 1.7 1.6 Expected return on plan assets (7.1 ) (8.2 ) (14.1 ) (16.3 ) (0.9 ) (1.1 ) (1.8 ) (2.2 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) — — — — Amortization of actuarial loss 4.0 3.8 7.9 7.5 0.3 0.3 0.7 0.6 $4.1 $2.8 $8.1 $5.5 $0.7 $0.5 $1.3 $0.9 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2019 2018 2019 2018 2019 2018 2019 2018 Service cost $0.8 $1.1 $1.7 $2.2 $0.3 $0.4 $0.6 $0.8 Interest cost 5.4 5.1 10.8 10.1 0.9 0.7 1.7 1.5 Expected return on plan assets (6.6 ) (7.6 ) (13.1 ) (15.2 ) (0.2 ) (0.1 ) (0.3 ) (0.3 ) Amortization of prior service credit — (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) (0.1 ) Amortization of actuarial loss 4.4 4.3 8.8 8.6 0.4 0.5 0.8 1.0 $4.0 $2.8 $8.1 $5.6 $1.3 $1.4 $2.7 $2.9
Recognized Compensation Expense And Income Tax Benefits	A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 2019 2018 Compensation expense $3.4 $5.1 $8.1 $8.4 $1.9 $2.8 $4.5 $4.6 $1.4 $2.1 $3.2 $3.4 Income tax benefits 1.0 1.5 2.3 2.4 0.5 0.9 1.3 1.4 0.4 0.5 0.9 0.9

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	6 Months Ended
	Jun. 30, 2019
Schedule of Asset Retirement Obligations [Line Items]
Reconciliation of Changes in Asset Retirement Obligations	A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the six months ended June 30, 2019 is as follows (in millions): Alliant Energy IPL Balance, January 1 $177.5 $118.3 Revisions in estimated cash flows (2.2 ) (2.2 ) Liabilities settled (1.4 ) (1.2 ) Liabilities incurred (a) 25.9 25.9 Accretion expense 3.4 2.2 Balance, June 30 $203.2 $143.0 (a) During the six months ended June 30 , 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.
IPL [Member]
Schedule of Asset Retirement Obligations [Line Items]
Reconciliation of Changes in Asset Retirement Obligations	A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the six months ended June 30, 2019 is as follows (in millions): Alliant Energy IPL Balance, January 1 $177.5 $118.3 Revisions in estimated cash flows (2.2 ) (2.2 ) Liabilities settled (1.4 ) (1.2 ) Liabilities incurred (a) 25.9 25.9 Accretion expense 3.4 2.2 Balance, June 30 $203.2 $143.0 (a) During the six months ended June 30 , 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2019
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of June 30, 2019 , gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 24,229 2019-2020 163,808 2019-2026 8,027 2019-2021 6,552 2019-2021 IPL 11,721 2019-2020 75,276 2019-2026 3,587 2019-2021 — — WPL 12,508 2019-2020 88,532 2019-2026 4,440 2019-2021 6,552 2019-2021
Fair Value Of Financial Instruments	Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $18.4 $24.6 $12.0 $16.1 $6.4 $8.5 Non-current derivative assets 3.5 3.7 1.9 1.6 1.6 2.1 Current derivative liabilities 12.9 5.6 5.8 3.1 7.1 2.5 Non-current derivative liabilities 15.1 17.7 6.4 8.1 8.7 9.6
IPL [Member]
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of June 30, 2019 , gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 24,229 2019-2020 163,808 2019-2026 8,027 2019-2021 6,552 2019-2021 IPL 11,721 2019-2020 75,276 2019-2026 3,587 2019-2021 — — WPL 12,508 2019-2020 88,532 2019-2026 4,440 2019-2021 6,552 2019-2021
Fair Value Of Financial Instruments	Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $18.4 $24.6 $12.0 $16.1 $6.4 $8.5 Non-current derivative assets 3.5 3.7 1.9 1.6 1.6 2.1 Current derivative liabilities 12.9 5.6 5.8 3.1 7.1 2.5 Non-current derivative liabilities 15.1 17.7 6.4 8.1 8.7 9.6
WPL [Member]
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of June 30, 2019 , gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 24,229 2019-2020 163,808 2019-2026 8,027 2019-2021 6,552 2019-2021 IPL 11,721 2019-2020 75,276 2019-2026 3,587 2019-2021 — — WPL 12,508 2019-2020 88,532 2019-2026 4,440 2019-2021 6,552 2019-2021
Fair Value Of Financial Instruments	Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $18.4 $24.6 $12.0 $16.1 $6.4 $8.5 Non-current derivative assets 3.5 3.7 1.9 1.6 1.6 2.1 Current derivative liabilities 12.9 5.6 5.8 3.1 7.1 2.5 Non-current derivative liabilities 15.1 17.7 6.4 8.1 8.7 9.6

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Statement [Line Items]
Fair Value Measurements	Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $161.8 $161.8 $— $— $161.8 $— $— $— $— $— Derivatives 21.9 — 8.2 13.7 21.9 28.3 — 8.9 19.4 28.3 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 28.0 — 27.5 0.5 28.0 23.3 — 16.1 7.2 23.3 Long-term debt (incl. current maturities) 6,144.9 — 6,788.8 2.1 6,790.9 5,502.8 — 5,858.4 2.4 5,860.8 IPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $13.9 $— $4.1 $9.8 $13.9 $17.7 $— $4.0 $13.7 $17.7 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 12.2 — 11.7 0.5 12.2 11.2 — 6.5 4.7 11.2 Long-term debt 2,850.5 — 3,135.3 — 3,135.3 2,552.3 — 2,691.2 — 2,691.2 WPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $160.4 $160.4 $— $— $160.4 $— $— $— $— $— Derivatives 8.0 — 4.1 3.9 8.0 10.6 — 4.9 5.7 10.6 Liabilities: Derivatives 15.8 — 15.8 — 15.8 12.1 — 9.6 2.5 12.1 Long-term debt (incl. current maturities) 2,181.8 — 2,498.2 — 2,498.2 1,834.9 — 2,043.7 — 2,043.7
Fair Value Measurements Using Significant Unobservable Inputs	Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.4 ($29.4 ) $178.3 $120.9 Total net losses included in changes in net assets (realized/unrealized) (0.1 ) (0.2 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Settlements (a) (4.8 ) (7.8 ) 36.3 87.4 Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 $— ($0.1 ) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $12.2 ($12.2 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (5.7 ) (10.0 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Sales (0.2 ) — — — Settlements (a) (10.8 ) (15.2 ) 95.2 (13.8 ) Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($2.6 ) ($9.7 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.6 ($15.4 ) $178.3 $120.9 Total net gains (losses) included in changes in net assets (realized/unrealized) 0.4 (1.6 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Settlements (a) (3.7 ) (6.4 ) 36.3 87.4 Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 $0.5 ($1.6 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $9.0 ($1.4 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (2.8 ) (9.2 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Sales (0.1 ) — — — Settlements (a) (8.8 ) (12.8 ) 95.2 (13.8 ) Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($0.9 ) ($9.0 ) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2019 2018 Beginning balance, April 1 ($0.2 ) ($14.0 ) Total net gains (losses) included in changes in net assets (realized/unrealized) (0.5 ) 1.4 Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Settlements (1.1 ) (1.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 ($0.5 ) $1.5 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2019 2018 Beginning balance, January 1 $3.2 ($10.8 ) Total net losses included in changes in net assets (realized/unrealized) (2.9 ) (0.8 ) Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Sales (0.1 ) — Settlements (2.0 ) (2.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($1.7 ) ($0.7 ) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2019 $2.4 $10.8 $1.4 $7.9 $1.0 $2.9 December 31, 2018 3.2 9.0 1.8 7.2 1.4 1.8
IPL [Member]
Statement [Line Items]
Fair Value Measurements	Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $161.8 $161.8 $— $— $161.8 $— $— $— $— $— Derivatives 21.9 — 8.2 13.7 21.9 28.3 — 8.9 19.4 28.3 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 28.0 — 27.5 0.5 28.0 23.3 — 16.1 7.2 23.3 Long-term debt (incl. current maturities) 6,144.9 — 6,788.8 2.1 6,790.9 5,502.8 — 5,858.4 2.4 5,860.8 IPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $13.9 $— $4.1 $9.8 $13.9 $17.7 $— $4.0 $13.7 $17.7 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 12.2 — 11.7 0.5 12.2 11.2 — 6.5 4.7 11.2 Long-term debt 2,850.5 — 3,135.3 — 3,135.3 2,552.3 — 2,691.2 — 2,691.2 WPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $160.4 $160.4 $— $— $160.4 $— $— $— $— $— Derivatives 8.0 — 4.1 3.9 8.0 10.6 — 4.9 5.7 10.6 Liabilities: Derivatives 15.8 — 15.8 — 15.8 12.1 — 9.6 2.5 12.1 Long-term debt (incl. current maturities) 2,181.8 — 2,498.2 — 2,498.2 1,834.9 — 2,043.7 — 2,043.7
Fair Value Measurements Using Significant Unobservable Inputs	Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.4 ($29.4 ) $178.3 $120.9 Total net losses included in changes in net assets (realized/unrealized) (0.1 ) (0.2 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Settlements (a) (4.8 ) (7.8 ) 36.3 87.4 Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 $— ($0.1 ) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $12.2 ($12.2 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (5.7 ) (10.0 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Sales (0.2 ) — — — Settlements (a) (10.8 ) (15.2 ) 95.2 (13.8 ) Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($2.6 ) ($9.7 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.6 ($15.4 ) $178.3 $120.9 Total net gains (losses) included in changes in net assets (realized/unrealized) 0.4 (1.6 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Settlements (a) (3.7 ) (6.4 ) 36.3 87.4 Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 $0.5 ($1.6 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $9.0 ($1.4 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (2.8 ) (9.2 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Sales (0.1 ) — — — Settlements (a) (8.8 ) (12.8 ) 95.2 (13.8 ) Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($0.9 ) ($9.0 ) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2019 2018 Beginning balance, April 1 ($0.2 ) ($14.0 ) Total net gains (losses) included in changes in net assets (realized/unrealized) (0.5 ) 1.4 Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Settlements (1.1 ) (1.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 ($0.5 ) $1.5 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2019 2018 Beginning balance, January 1 $3.2 ($10.8 ) Total net losses included in changes in net assets (realized/unrealized) (2.9 ) (0.8 ) Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Sales (0.1 ) — Settlements (2.0 ) (2.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($1.7 ) ($0.7 ) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2019 $2.4 $10.8 $1.4 $7.9 $1.0 $2.9 December 31, 2018 3.2 9.0 1.8 7.2 1.4 1.8
WPL [Member]
Statement [Line Items]
Fair Value Measurements	Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $161.8 $161.8 $— $— $161.8 $— $— $— $— $— Derivatives 21.9 — 8.2 13.7 21.9 28.3 — 8.9 19.4 28.3 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 28.0 — 27.5 0.5 28.0 23.3 — 16.1 7.2 23.3 Long-term debt (incl. current maturities) 6,144.9 — 6,788.8 2.1 6,790.9 5,502.8 — 5,858.4 2.4 5,860.8 IPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $13.9 $— $4.1 $9.8 $13.9 $17.7 $— $4.0 $13.7 $17.7 Deferred proceeds 214.6 — — 214.6 214.6 119.4 — — 119.4 119.4 Liabilities: Derivatives 12.2 — 11.7 0.5 12.2 11.2 — 6.5 4.7 11.2 Long-term debt 2,850.5 — 3,135.3 — 3,135.3 2,552.3 — 2,691.2 — 2,691.2 WPL June 30, 2019 December 31, 2018 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $160.4 $160.4 $— $— $160.4 $— $— $— $— $— Derivatives 8.0 — 4.1 3.9 8.0 10.6 — 4.9 5.7 10.6 Liabilities: Derivatives 15.8 — 15.8 — 15.8 12.1 — 9.6 2.5 12.1 Long-term debt (incl. current maturities) 2,181.8 — 2,498.2 — 2,498.2 1,834.9 — 2,043.7 — 2,043.7
Fair Value Measurements Using Significant Unobservable Inputs	Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.4 ($29.4 ) $178.3 $120.9 Total net losses included in changes in net assets (realized/unrealized) (0.1 ) (0.2 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Settlements (a) (4.8 ) (7.8 ) 36.3 87.4 Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 $— ($0.1 ) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $12.2 ($12.2 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (5.7 ) (10.0 ) — — Transfers out of Level 3 3.9 — — — Purchases 13.8 26.7 — — Sales (0.2 ) — — — Settlements (a) (10.8 ) (15.2 ) 95.2 (13.8 ) Ending balance, June 30 $13.2 ($10.7 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($2.6 ) ($9.7 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2019 2018 2019 2018 Beginning balance, April 1 $0.6 ($15.4 ) $178.3 $120.9 Total net gains (losses) included in changes in net assets (realized/unrealized) 0.4 (1.6 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Settlements (a) (3.7 ) (6.4 ) 36.3 87.4 Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 $0.5 ($1.6 ) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2019 2018 2019 2018 Beginning balance, January 1 $9.0 ($1.4 ) $119.4 $222.1 Total net losses included in changes in net assets (realized/unrealized) (2.8 ) (9.2 ) — — Transfers out of Level 3 2.5 — — — Purchases 9.5 19.3 — — Sales (0.1 ) — — — Settlements (a) (8.8 ) (12.8 ) 95.2 (13.8 ) Ending balance, June 30 $9.3 ($4.1 ) $214.6 $208.3 The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($0.9 ) ($9.0 ) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2019 2018 Beginning balance, April 1 ($0.2 ) ($14.0 ) Total net gains (losses) included in changes in net assets (realized/unrealized) (0.5 ) 1.4 Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Settlements (1.1 ) (1.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30 ($0.5 ) $1.5 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2019 2018 Beginning balance, January 1 $3.2 ($10.8 ) Total net losses included in changes in net assets (realized/unrealized) (2.9 ) (0.8 ) Transfers out of Level 3 1.4 — Purchases 4.3 7.4 Sales (0.1 ) — Settlements (2.0 ) (2.4 ) Ending balance, June 30 $3.9 ($6.6 ) The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at June 30 ($1.7 ) ($0.7 ) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2019 $2.4 $10.8 $1.4 $7.9 $1.0 $2.9 December 31, 2018 3.2 9.0 1.8 7.2 1.4 1.8

Commitments And Contingencies (

Commitments And Contingencies (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At June 30, 2019 , the related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Purchased power (a) $184 $183 $1 Natural gas 925 460 465 Coal (b) 130 81 49 Other (c) 88 49 28 $1,327 $773 $543 (a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million . (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change. (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 .
MGP Site Estimated Future Costs And Recorded Liabilities	At June 30, 2019 , estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At June 30, 2019 , such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $15 - $31 $12 - $26 Current and non-current environmental liabilities 19 16
IPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At June 30, 2019 , the related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Purchased power (a) $184 $183 $1 Natural gas 925 460 465 Coal (b) 130 81 49 Other (c) 88 49 28 $1,327 $773 $543 (a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million . (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change. (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 .
MGP Site Estimated Future Costs And Recorded Liabilities	At June 30, 2019 , estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At June 30, 2019 , such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $15 - $31 $12 - $26 Current and non-current environmental liabilities 19 16
WPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At June 30, 2019 , the related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Purchased power (a) $184 $183 $1 Natural gas 925 460 465 Coal (b) 130 81 49 Other (c) 88 49 28 $1,327 $773 $543 (a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million . (b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change. (c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 .

Segments Of Business (Tables)

Segments Of Business (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting Information [Line Items]
Schedule Of Segments Of Business	Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations. ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended June 30, 2019 Revenues $691.2 $65.2 $10.9 $767.3 $22.9 $790.2 Operating income 132.9 7.2 1.4 141.5 8.3 149.8 Net income attributable to Alliant Energy common shareowners 87.0 7.6 94.6 Three Months Ended June 30, 2018 Revenues $726.3 $68.6 $10.7 $805.6 $10.5 $816.1 Operating income 134.8 5.4 0.9 141.1 10.1 151.2 Net income attributable to Alliant Energy common shareowners 91.5 8.9 100.4 ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2019 Revenues $1,434.6 $281.0 $22.0 $1,737.6 $39.8 $1,777.4 Operating income 259.3 52.4 1.4 313.1 13.5 326.6 Net income attributable to Alliant Energy common shareowners 206.0 13.7 219.7 Six Months Ended June 30, 2018 Revenues $1,435.0 $254.2 $23.9 $1,713.1 $19.3 $1,732.4 Operating income 261.5 36.9 2.3 300.7 16.2 316.9 Net income attributable to Alliant Energy common shareowners 192.2 29.1 221.3
IPL [Member]
Segment Reporting Information [Line Items]
Schedule Of Segments Of Business	Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $392.3 $38.4 $10.5 $441.2 Operating income 68.9 4.2 1.4 74.5 Earnings available for common stock 45.0 Three Months Ended June 30, 2018 Revenues $422.1 $42.2 $10.5 $474.8 Operating income 73.5 2.5 1.7 77.7 Earnings available for common stock 51.7 Six Months Ended June 30, 2019 Revenues $812.1 $163.0 $21.2 $996.3 Operating income 115.7 30.5 1.8 148.0 Earnings available for common stock 98.3 Six Months Ended June 30, 2018 Revenues $827.8 $150.3 $22.5 $1,000.6 Operating income 131.0 19.4 2.9 153.3 Earnings available for common stock 98.4
WPL [Member]
Segment Reporting Information [Line Items]
Schedule Of Segments Of Business	Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations. Electric Gas Other Total (in millions) Three Months Ended June 30, 2019 Revenues $298.9 $26.8 $0.4 $326.1 Operating income 64.0 3.0 — 67.0 Earnings available for common stock 42.0 Three Months Ended June 30, 2018 Revenues $304.2 $26.4 $0.2 $330.8 Operating income (loss) 61.3 2.9 (0.8 ) 63.4 Earnings available for common stock 39.8 Six Months Ended June 30, 2019 Revenues $622.5 $118.0 $0.8 $741.3 Operating income (loss) 143.6 21.9 (0.4 ) 165.1 Earnings available for common stock 107.7 Six Months Ended June 30, 2018 Revenues $607.2 $103.9 $1.4 $712.5 Operating income (loss) 130.5 17.5 (0.6 ) 147.4 Earnings available for common stock 93.8

Related Parties (Tables)

Related Parties (Tables)	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Line Items]
Services Provided, Sales Credited And Purchases	The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 Corporate Services billings $47 $44 $90 $85 $35 $34 $68 $67 Sales credited 12 18 27 23 3 8 4 9 Purchases billed 74 80 158 173 29 20 59 37
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2019 December 31, 2018 June 30, 2019 December 31, 2018 Net payables to Corporate Services $108 $95 $72 $71
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 ATC billings to WPL $27 $26 $54 $53 WPL billings to ATC 3 3 7 5
IPL [Member]
Related Party Transactions [Line Items]
Services Provided, Sales Credited And Purchases	The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 Corporate Services billings $47 $44 $90 $85 $35 $34 $68 $67 Sales credited 12 18 27 23 3 8 4 9 Purchases billed 74 80 158 173 29 20 59 37
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2019 December 31, 2018 June 30, 2019 December 31, 2018 Net payables to Corporate Services $108 $95 $72 $71
WPL [Member]
Related Party Transactions [Line Items]
Services Provided, Sales Credited And Purchases	The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2019 2018 2019 2018 2019 2018 2019 2018 Corporate Services billings $47 $44 $90 $85 $35 $34 $68 $67 Sales credited 12 18 27 23 3 8 4 9 Purchases billed 74 80 158 173 29 20 59 37
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2019 December 31, 2018 June 30, 2019 December 31, 2018 Net payables to Corporate Services $108 $95 $72 $71
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2019 2018 2019 2018 ATC billings to WPL $27 $26 $54 $53 WPL billings to ATC 3 3 7 5

Summary Of Significant Accoun_3

Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 161.8		$ 0
Money market fund investments interest rate, percentage	2.40%
Increase in operating cash flows from change in method of presentation to daily transactional activity		$ 339.4
Net cash flows from operating activities	$ 276.9	274.4
IPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in operating cash flows from change in method of presentation to daily transactional activity		339.4
Net cash flows from operating activities	89	12.8
WPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 160.4		$ 0
Money market fund investments interest rate, percentage	2.40%
Net cash flows from operating activities	$ 208.2	$ 225.9

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2019	Dec. 31, 2020
2020 Forward Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Requested rate annual increase, amount		$ 204
Interim rate annual increase, amount		90
2020 Forward Test Period Retail Gas [Member] | IPL [Member]
Regulatory Matters [Line Items]
Requested rate annual increase, amount		$ 21
Forecast [Member] | 2020 Forward Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Requested rate annual increase, amount			$ 114
DAEC PPA [Member]
Regulatory Matters [Line Items]
PPA term amendment		5 years
Recovery period, authorized		5 years
DAEC PPA [Member] | Forecast [Member]
Regulatory Matters [Line Items]
Buyout payment	$ 110

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Regulatory assets	$ 1,806.9	$ 1,737.3
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	815.5	820.6
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	522.9	542.3
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	111	110.8
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	107.1	0
EGUs retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	102.8	111.6
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	30.6	28
Emission allowances [Member]
Regulatory Assets [Line Items]
Regulatory assets	22.4	23.6
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	94.6	100.4
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,364.5	1,279
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	780.2	783.1
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	264.7	274
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	76.2	76.3
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	107.1	0
IPL [Member] | EGUs retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	51.7	55.4
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	13.4	15.1
IPL [Member] | Emission allowances [Member]
Regulatory Assets [Line Items]
Regulatory assets	22.4	23.6
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	48.8	51.5
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	442.4	458.3
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	35.3	37.5
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	258.2	268.3
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	34.8	34.5
WPL [Member] | EGUs retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	51.1	56.2
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	17.2	12.9
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 45.8	$ 48.9

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,442.9	$ 1,493.2
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	853.8	890.6
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	399.2	401.2
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	101.5	104
WPL's earnings sharing mechanism [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	25.2	25.4
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	22.7	16.8
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	40.5	55.2
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	719.9	754.9
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	365.6	390.1
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	269.5	273.3
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	52.7	47.7
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	11.9	11.9
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	20.2	31.9
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	723	738.3
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	488.2	500.5
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	129.7	127.9
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	48.8	56.3
WPL [Member] | WPL's earnings sharing mechanism [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	25.2	25.4
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	10.8	4.9
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 20.3	$ 23.3

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) - Receivables Sold [Member] - IPL [Member] $ in Millions	Jun. 30, 2019USD ($)
Receivables [Line Items]
Available capacity	$ 83
Outstanding receivables past due	$ 27.1

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Maximum [Member]
Receivables [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 25	$ 116	$ 108	$ 116
Average [Member]
Receivables [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 2.6	$ 52.3	$ 41.6	$ 56.7

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Receivables [Line Items]
Fair value of deferred proceeds	$ 214.6	$ 119.4
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	214.6	119.4
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	138.3	140.1
Unbilled utility revenues	90.5	97.1
Other receivables	0.4	0.1
Receivables sold to third party	229.2	237.3
Less: cash proceeds	5	108
Deferred proceeds	224.2	129.3
Less: allowance for doubtful accounts	9.6	9.9
Fair value of deferred proceeds	$ 214.6	$ 119.4

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Receivables [Line Items]
Collections	$ 487.7	$ 483.7	$ 1,043.5	$ 1,000.7
Write-offs, net of recoveries	$ 2.6	$ 1.9	$ 8.1	$ 8

Investments and Acquisitions (N

Investments and Acquisitions (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Schedule of Investments [Line Items]
Acquisitions of freight management companies	$ 21
Contingent consideration	$ 8
Contingent consideration, expected payment timing	2 years

Investments and Acquisitions (U

Investments and Acquisitions (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (12.7)	$ (10.5)	$ (23.6)	$ (31.8)
ATC Holdings [Member]
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(10)	(7.8)	(19.5)	(16.5)
Non-utility wind farm In Oklahoma [Member]
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(1.3)	(2.5)	(2.4)	(14.6)
Other [Member]
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (1.4)	$ (0.2)	$ (1.7)	$ (0.7)

Common Equity (Narrative) (Deta

Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Common Equity [Line Items]
Proceeds from issuance of common stock, net		$ 6	$ 93.8	$ 60.6	$ 100.1
Comprehensive income (loss)		(1.4)	0.6	(0.7)	0.6
IPL [Member]
Common Equity [Line Items]
Comprehensive income (loss)		0	0	0	0
WPL [Member]
Common Equity [Line Items]
Comprehensive income (loss)		$ 0	$ 0	$ 0	$ 0
Equity Forward Agreements [Member]
Common Equity [Line Items]
Common stock issued during the period, equity forward agreements (in shares)				1,090,300
Forward sales price (in dollars per share)		$ 44.13		$ 44.13			$ 44.33
Proceeds from issuance of common stock, net				$ 48
Shares included in diluted earnings per share (in shares)				559,597
Forecast [Member] | Equity Forward Agreements [Member]
Common Equity [Line Items]
Common stock issued during the period, equity forward agreements (in shares)						8,358,973
Subsequent Event [Member] | Equity Forward Agreements [Member]
Common Equity [Line Items]
Common stock issued during the period, equity forward agreements (in shares)	1,500,000
Forward sales price (in dollars per share)	$ 44.06
Proceeds from issuance of common stock, net	$ 66

Common Equity (Common Share Act

Common Equity (Common Share Activity) (Details)	6 Months Ended
	Jun. 30, 2019shares
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1, 2019 (in shares)	236,063,279
Shareowner Direct Plan issuances (in shares)	268,755
Equity-based compensation plans (in shares)	101,478
Other (in shares)	(2,738)
Shares outstanding, June 30, 2019 (in shares)	237,521,074
Equity Forward Agreements [Member]
Common Stock Oustanding [Roll Forward]
Equity forward agreements (in shares)	1,090,300

Common Equity (Changes in Share

Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			$ 4,585.7
Beginning balance	$ 4,882.4	$ 4,431.5	4,785.7	$ 4,382.2
Net income attributable to common shareowners	94.6	100.4	219.7	221.3
Common stock dividends	(84.1)	(77.3)	(167.8)	(154.8)
Equity forward settlements, At-the-market Offering Program and Shareowner Direct Plan issuances	6	93.8	60.6	100.1
Equity-based compensation plans and other	2.1	1.7	2.1	1.3
Other comprehensive income (loss), net of tax	(1.4)	0.6	(0.7)	0.6
Ending balance	4,699.6		4,699.6
Ending balance	$ 4,899.6	$ 4,550.7	$ 4,899.6	$ 4,550.7
Common stock dividends (in dollars per share)	$ 0.355	$ 0.335	$ 0.71	$ 0.67
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 2.4	$ 2.3	$ 2.4	$ 2.3
Ending balance	2.4	2.3	2.4	2.3
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,100	1,851.4	2,045.5	1,845.5
Equity forward settlements, At-the-market Offering Program and Shareowner Direct Plan issuances	6	93.8	60.6	100.1
Equity-based compensation plans and other	2.4	2	2.3	1.6
Ending balance	2,108.4	1,947.2	2,108.4	1,947.2
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,587.3	2,389.4	2,545.9	2,346
Net income attributable to common shareowners	94.6	100.4	219.7	221.3
Common stock dividends	(84.1)	(77.3)	(167.8)	(154.8)
Ending balance	2,597.8	2,412.5	2,597.8	2,412.5
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2.4	(0.5)	1.7	(0.5)
Other comprehensive income (loss), net of tax	(1.4)	0.6	(0.7)	0.6
Ending balance	1	0.1	1	0.1
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(9.7)	(11.1)	(9.8)	(11.1)
Equity-based compensation plans and other	(0.3)	(0.3)	(0.2)	(0.3)
Ending balance	(10)	(11.4)	(10)	(11.4)
Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	200	200	200	200
Ending balance	200	200	200	200
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,030.7
Beginning balance	3,342	2,714.5	3,230.7	2,709.7
Net income attributable to common shareowners	45	51.7	98.3	98.4
Common stock dividends	(41.9)	(42.1)	(83.9)	(84)
Capital contributions from parent		130	100	130
Other comprehensive income (loss), net of tax	0	0	0	0
Ending balance	3,145.1		3,145.1
Ending balance	3,345.1	2,854.1	3,345.1	2,854.1
IPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	33.4	33.4	33.4	33.4
Ending balance	33.4	33.4	33.4	33.4
IPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,322.8	1,797.8	2,222.8	1,797.8
Capital contributions from parent		130	100	130
Ending balance	2,322.8	1,927.8	2,322.8	1,927.8
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	785.8	683.3	774.5	678.5
Net income attributable to common shareowners	45	51.7	98.3	98.4
Common stock dividends	(41.9)	(42.1)	(83.9)	(84)
Ending balance	788.9	692.9	788.9	692.9
IPL [Member] | Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	200	200	200	200
Ending balance	200	200	200	200
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			2,149.5
Beginning balance	2,179.2	1,900.5	2,149.5	1,881.5
Net income attributable to common shareowners	42	39.8	107.7	93.8
Common stock dividends	(36)	(35.1)	(72)	(70.1)
Capital contributions from parent		150	0	150
Other comprehensive income (loss), net of tax	0	0	0	0
Ending balance	2,185.2		2,185.2
Ending balance	2,185.2	2,055.2	2,185.2	2,055.2
WPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	66.2	66.2	66.2	66.2
Ending balance	66.2	66.2	66.2	66.2
WPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,309	1,109	1,309	1,109
Capital contributions from parent		150		150
Ending balance	1,309	1,259	1,309	1,259
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	804	725.3	774.3	706.3
Net income attributable to common shareowners	42	39.8	107.7	93.8
Common stock dividends	(36)	(35.1)	(72)	(70.1)
Ending balance	$ 810	$ 730	$ 810	$ 730

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($)	1 Months Ended			6 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Apr. 30, 2019	Jun. 30, 2019	Jun. 30, 2018
Debt [Line Items]
Credit facility agreement, extension				1 year
Line of credit facility, current borrowing capacity		$ 1,000,000,000		$ 1,000,000,000
Payments to retire long-term debt				3,400,000	$ 503,000,000
IPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity		250,000,000		250,000,000
WPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity		300,000,000		$ 300,000,000
Senior Debentures [Member] | 3.6% senior debentures due 2029 [Member] | IPL [Member]
Debt [Line Items]
Proceeds from issuance of long-term debt			$ 300,000,000
Interest rate, percent			3.60%
Debentures [Member] | 3% debentures due 2029 [Member] | WPL [Member]
Debt [Line Items]
Proceeds from issuance of long-term debt		$ 350,000,000
Interest rate, percent		3.00%		3.00%
Debentures [Member] | 5% debentures due 2019 [Member] | WPL [Member]
Debt [Line Items]
Interest rate, percent		5.00%		5.00%
Parent Company [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity		$ 450,000,000		$ 450,000,000
Subsequent Event [Member] | Debentures [Member] | 5% debentures due 2019 [Member] | WPL [Member]
Debt [Line Items]
Payments to retire long-term debt	$ 250,000,000

Debt (Credit Facilities) (Detai

Debt (Credit Facilities) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Debt [Line Items]
Commercial paper outstanding	$ 390.5	$ 441.2
Commercial paper weighted average interest rates	2.60%
Available credit facility capacity	$ 609.5
IPL [Member]
Debt [Line Items]
Commercial paper outstanding	0	50.4
Available credit facility capacity	250
WPL [Member]
Debt [Line Items]
Commercial paper outstanding	0	$ 105.5
Available credit facility capacity	$ 300

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 590.2	$ 446.5	$ 600.6	$ 446.5
Average amount outstanding (based on daily outstanding balances)	$ 531.7	$ 234.5	$ 515.4	$ 272.1
Weighted average interest rates	2.70%	2.20%	2.70%	2.00%
IPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 0	$ 31.4	$ 50.4	$ 31.4
Average amount outstanding (based on daily outstanding balances)	0	$ 5.1	$ 0.3	$ 2.6
Weighted average interest rates		2.30%	2.80%	2.30%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	193.3	$ 109.4	$ 195.1	$ 109.4
Average amount outstanding (based on daily outstanding balances)	$ 141.6	$ 45.2	$ 139.8	$ 28.4
Weighted average interest rates	2.50%	1.80%	2.50%	1.80%

Leases (Narrative) (Details)

Leases (Narrative) (Details)	12 Months Ended
	Dec. 31, 2005lease_renewal_period_option
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance leases, renewal options (in number of renewal periods)	2

Leases (Operating Leases) (Deta

Leases (Operating Leases) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 17	$ 17
Operating leases liabilities, Other current liabilities	2	2
Operating leases liabilities, Other liabilities	15	15
Operating leases liabilities, Total	$ 17	$ 17
Operating Lease, Weighted Average Remaining Lease Term	11 years	11 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 1
IPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	10	10
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	9	9
Operating leases liabilities, Total	$ 10	$ 10
Operating Lease, Weighted Average Remaining Lease Term	13 years	13 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 0
WPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	7	7
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	6	6
Operating leases liabilities, Total	$ 7	$ 7
Operating Lease, Weighted Average Remaining Lease Term	10 years	10 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 0

Leases (Finance Lease) (Details

Leases (Finance Lease) (Details) - WPL [Member] - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Leases [Line Items]
Finance lease liabilities, Sheboygan Falls Energy Facility	$ 55.8	$ 55.8	$ 60
Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	35	35
Finance lease liabilities, Other current liabilities	8	8
Finance lease liabilities, Sheboygan Falls Energy Facility	56	56
Finance lease liabilities, Total	$ 64	$ 64
Finance Lease, Weighted Average Remaining Lease Term	6 years	6 years
Finance lease, Discount rate, percent	11.00%	11.00%
Finance lease, Depreciation expense	$ 2	$ 3
Finance lease, Interest expense	2	4
Finance lease, Total expense	$ 4	$ 7

Leases (Expected Maturities of

Leases (Expected Maturities of Operating and Finance Lease Liabilities (Details) $ in Millions	Jun. 30, 2019USD ($)
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	$ 2
Operating Leases Liability, 2020	2
Operating Leases Liability, 2021	2
Operating Leases Liability, 2022	2
Operating Leases Liability, 2023	2
Operating Leases Liability, Thereafter	13
Operating Leases Liability, Total	23
Operating Leases Liability, Less: amount representing interest	6
Operating Leases Liability, Present value of minimum lease payments	17
IPL [Member]
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	1
Operating Leases Liability, 2020	1
Operating Leases Liability, 2021	1
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, Thereafter	9
Operating Leases Liability, Total	14
Operating Leases Liability, Less: amount representing interest	4
Operating Leases Liability, Present value of minimum lease payments	10
WPL [Member]
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	1
Operating Leases Liability, 2020	1
Operating Leases Liability, 2021	1
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, Thereafter	4
Operating Leases Liability, Total	9
Operating Leases Liability, Less: amount representing interest	2
Operating Leases Liability, Present value of minimum lease payments	7
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance Lease Liability, Remainder of 2019	7
Finance Lease Liability, 2020	15
Finance Lease Liability, 2021	15
Finance Lease Liability, 2022	15
Finance Lease Liability, 2023	15
Finance Lease Liability, Thereafter	20
Finance Lease Liability, Total	87
Finance Lease Liability, Less: amount representing interest	23
Finance Lease Liability, Present value of minimum lease payments	$ 64

Leases (Future Minimum Operatin

Leases (Future Minimum Operating and Capital Lease Payments) (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases [Line Items]
Operating Leases, 2019	$ 5
Operating Leases, 2020	5
Operating Leases, 2021	3
Operating Leases, 2022	3
Operating Leases, 2023	2
Operating Leases, Thereafter	12
Operating Leases, Total	30
IPL [Member]
Leases [Line Items]
Operating Leases, 2019	3
Operating Leases, 2020	2
Operating Leases, 2021	2
Operating Leases, 2022	2
Operating Leases, 2023	2
Operating Leases, Thereafter	12
Operating Leases, Total	23
WPL [Member]
Leases [Line Items]
Operating Leases, 2019	2
Operating Leases, 2020	3
Operating Leases, 2021	1
Operating Leases, 2022	0
Operating Leases, 2023	0
Operating Leases, Thereafter	0
Operating Leases, Total	6
WPL [Member] | Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Capital Leases, 2019	15
Capital Leases, 2020	15
Capital Leases, 2021	15
Capital Leases, 2022	15
Capital Leases, 2023	15
Capital Leases, Thereafter	19
Capital Leases, Total	94
Capital Leases, Less: amount representing interest	26
Capital Leases, Present value of minimum capital lease payments	$ 68

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 790.2	$ 816.1	$ 1,777.4	$ 1,732.4
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	691.2	726.3	1,434.6	1,435
Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	233.3	248.3	508	507.7
Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	171.3	172.3	352.4	346.3
Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	214.2	225.4	422.9	427.3
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	41	43.1	87.5	96.9
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	31.4	37.2	63.8	56.8
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	65.2	68.6	281	254.2
Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	35.2	37.7	167	148.3
Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16.1	19.3	79.7	76.3
Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2.6	7.4	8.4
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11.9	9	26.9	21.2
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10.9	10.7	22	23.9
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9.2	8.4	17.6	17.8
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1.7	2.3	4.4	6.1
Non-utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22.9	10.5	39.8	19.3
Non-utility and Other [Member] | Transportation and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22.9	10.5	39.8	19.3
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	441.2	474.8	996.3	1,000.6
IPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	392.3	422.1	812.1	827.8
IPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	125.9	139.3	273.4	281.5
IPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	111.4	114.2	228	225.8
IPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	118.4	128.8	234.5	243.6
IPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14.6	13.9	31.5	38.2
IPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	25.9	44.7	38.7
IPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	38.4	42.2	163	150.3
IPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20	22.8	97.9	88.3
IPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8.8	11.8	43.6	43.4
IPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1.6	1.4	4.8	4.1
IPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8	6.2	16.7	14.5
IPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10.5	10.5	21.2	22.5
IPL [Member] | Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9.2	8.4	17.6	17.8
IPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1.3	2.1	3.6	4.7
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	326.1	330.8	741.3	712.5
WPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	298.9	304.2	622.5	607.2
WPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	107.4	109	234.6	226.2
WPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	59.9	58.1	124.4	120.5
WPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	95.8	96.6	188.4	183.7
WPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	26.4	29.2	56	58.7
WPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9.4	11.3	19.1	18.1
WPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	26.8	26.4	118	103.9
WPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	15.2	14.9	69.1	60
WPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7.3	7.5	36.1	32.9
WPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0.4	1.2	2.6	4.3
WPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3.9	2.8	10.2	6.7
WPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0.4	0.2	0.8	1.4
WPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0.4	$ 0.2	$ 0.8	$ 1.4

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	7.50%	6.50%	7.20%	7.10%
Production tax credits	(8.50%)	(5.40%)	(8.90%)	(5.50%)
Effect of rate-making on property-related differences	(6.20%)	(6.70%)	(6.00%)	(7.20%)
Amortization of excess deferred taxes	(1.30%)	(0.40%)	(1.10%)	(0.40%)
IPL's tax benefit riders	(0.70%)	(2.10%)	(0.70%)	(2.20%)
Other items, net	(1.50%)	(1.20%)	(1.00%)	(1.00%)
Overall income tax rate	10.30%	11.70%	10.50%	11.80%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	8.30%	7.00%	8.10%	7.70%
Production tax credits	(13.20%)	(5.30%)	(13.60%)	(5.30%)
Effect of rate-making on property-related differences	(10.10%)	(11.50%)	(9.60%)	(12.40%)
Amortization of excess deferred taxes	(0.40%)	0.00%	(0.30%)	0.00%
IPL's tax benefit riders	(1.40%)	(4.30%)	(1.40%)	(4.50%)
Other items, net	(0.40%)	(2.80%)	(0.50%)	(1.50%)
Overall income tax rate	3.80%	4.10%	3.70%	5.00%
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	6.20%	6.20%	6.20%	6.20%
Production tax credits	(4.20%)	(6.80%)	(4.60%)	(6.70%)
Effect of rate-making on property-related differences	(2.70%)	(2.70%)	(2.40%)	(2.50%)
Amortization of excess deferred taxes	(2.30%)	(0.10%)	(1.80%)	(0.10%)
Other items, net	(2.50%)	(4.10%)	(1.20%)	(1.90%)
Overall income tax rate	15.50%	13.50%	17.20%	16.00%

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Jun. 30, 2019USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 760
Tax credits, carryforward amount	325
Federal [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	550
Tax credits, carryforward amount	152
Federal [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	122
Tax credits, carryforward amount	154
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	764
State [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	13
State [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)$ / sharesshares
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost | $	$ 10.3
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	1 year
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	2 years
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost | $	$ 5.7
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost | $	$ 4.2
Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Performance period	3 years
Granted (in shares/awards)	80,837
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 46.35
Performance Shares [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0.00%
Performance Shares [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200.00%
Performance Restricted Stock Unit [Member]
Defined Benefit Plan Disclosure [Line Items]
Performance period	3 years
Granted (in shares/awards)	80,837
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 45.63
Instrument valuation based on shares of common stock, number of shares	1
Performance Restricted Stock Unit [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0.00%
Performance Restricted Stock Unit [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200.00%
Restricted Stock Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Performance period	3 years
Granted (in shares/awards)	95,938
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 45.63
Instrument valuation based on shares of common stock, number of shares	1

Benefit Plans (Defined Benefit

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2.4	$ 3	$ 4.8	$ 6
Interest cost	12.4	11.7	24.9	23.4
Expected return on plan assets	(15)	(17.5)	(30)	(34.9)
Amortization of prior service credit	(0.1)	(0.1)	(0.3)	(0.3)
Amortization of actuarial loss	9.1	8.8	18.2	17.6
Total	8.8	5.9	17.6	11.8
OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.9	1	1.7	2.1
Interest cost	2.1	1.9	4.2	3.8
Expected return on plan assets	(1.3)	(1.5)	(2.5)	(3)
Amortization of prior service credit	(0.1)	(0.1)	(0.1)	(0.1)
Amortization of actuarial loss	0.8	0.9	1.6	1.7
Total	2.4	2.2	4.9	4.5
IPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.5	1.9	3	3.7
Interest cost	5.7	5.4	11.4	10.7
Expected return on plan assets	(7.1)	(8.2)	(14.1)	(16.3)
Amortization of prior service credit	0	(0.1)	(0.1)	(0.1)
Amortization of actuarial loss	4	3.8	7.9	7.5
Total	4.1	2.8	8.1	5.5
IPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.4	0.5	0.7	0.9
Interest cost	0.9	0.8	1.7	1.6
Expected return on plan assets	(0.9)	(1.1)	(1.8)	(2.2)
Amortization of prior service credit	0	0	0	0
Amortization of actuarial loss	0.3	0.3	0.7	0.6
Total	0.7	0.5	1.3	0.9
WPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.8	1.1	1.7	2.2
Interest cost	5.4	5.1	10.8	10.1
Expected return on plan assets	(6.6)	(7.6)	(13.1)	(15.2)
Amortization of prior service credit	0	(0.1)	(0.1)	(0.1)
Amortization of actuarial loss	4.4	4.3	8.8	8.6
Total	4	2.8	8.1	5.6
WPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.3	0.4	0.6	0.8
Interest cost	0.9	0.7	1.7	1.5
Expected return on plan assets	(0.2)	(0.1)	(0.3)	(0.3)
Amortization of prior service credit	(0.1)	(0.1)	(0.1)	(0.1)
Amortization of actuarial loss	0.4	0.5	0.8	1
Total	$ 1.3	$ 1.4	$ 2.7	$ 2.9

Benefit Plans (Recognized Compe

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Compensation expense	$ 3.4	$ 5.1	$ 8.1	$ 8.4
Income tax benefits	1	1.5	2.3	2.4
IPL [Member]
Compensation expense	1.9	2.8	4.5	4.6
Income tax benefits	0.5	0.9	1.3	1.4
WPL [Member]
Compensation expense	1.4	2.1	3.2	3.4
Income tax benefits	$ 0.4	$ 0.5	$ 0.9	$ 0.9

Asset Retirement Obligations (R

Asset Retirement Obligations (Reconciliation Of Changes In Asset Retirement Obligations) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	$ 177.5
Revisions in estimated cash flows	(2.2)
Liabilities settled	(1.4)
Liabilities incurred	25.9	[1]
Accretion expense	3.4
Balance, June 30	203.2
IPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	118.3
Revisions in estimated cash flows	(2.2)
Liabilities settled	(1.2)
Liabilities incurred	25.9	[1]
Accretion expense	2.2
Balance, June 30	$ 143
[1]	During the six months ended June 30 , 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] gal in Thousands, T in Thousands, MWh in Thousands, Dekatherms in Thousands	6 Months Ended
	Jun. 30, 2019DekathermsMWhTgal
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	24,229
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	11,721
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	12,508
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	163,808
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	75,276
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	88,532
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	8,027
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	3,587
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	4,440
Diesel Fuel (Gallons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	6,552
Diesel Fuel (Gallons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	0
Diesel Fuel (Gallons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	6,552

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 18.4	$ 24.6
Non-current derivative assets	3.5	3.7
Current derivative liabilities	12.9	5.6
Non-current derivative liabilities	15.1	17.7
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	12	16.1
Non-current derivative assets	1.9	1.6
Current derivative liabilities	5.8	3.1
Non-current derivative liabilities	6.4	8.1
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	6.4	8.5
Non-current derivative assets	1.6	2.1
Current derivative liabilities	7.1	2.5
Non-current derivative liabilities	$ 8.7	$ 9.6

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets:
Money market fund investments	$ 161.8	$ 0
Deferred proceeds	214.6	119.4
Liabilities:
Long-term debt (incl. current maturities)	6,790.9	5,860.8
IPL [Member]
Assets:
Deferred proceeds	214.6	119.4
Liabilities:
Long-term debt (incl. current maturities)	3,135.3	2,691.2
WPL [Member]
Assets:
Money market fund investments	160.4	0
Liabilities:
Long-term debt (incl. current maturities)	2,498.2	2,043.7
Commodity Contracts [Member]
Assets:
Derivatives	21.9	28.3
Liabilities:
Derivatives	28	23.3
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	13.9	17.7
Liabilities:
Derivatives	12.2	11.2
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	8	10.6
Liabilities:
Derivatives	15.8	12.1
Level 1 [Member]
Assets:
Money market fund investments	161.8	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | WPL [Member]
Assets:
Money market fund investments	160.4	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	6,788.8	5,858.4
Level 2 [Member] | IPL [Member]
Assets:
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,135.3	2,691.2
Level 2 [Member] | WPL [Member]
Assets:
Money market fund investments	0	0
Liabilities:
Long-term debt (incl. current maturities)	2,498.2	2,043.7
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	8.2	8.9
Liabilities:
Derivatives	27.5	16.1
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	4.1	4
Liabilities:
Derivatives	11.7	6.5
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	4.1	4.9
Liabilities:
Derivatives	15.8	9.6
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	214.6	119.4
Liabilities:
Long-term debt (incl. current maturities)	2.1	2.4
Level 3 [Member] | IPL [Member]
Assets:
Deferred proceeds	214.6	119.4
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | WPL [Member]
Assets:
Money market fund investments	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	13.7	19.4
Liabilities:
Derivatives	0.5	7.2
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	9.8	13.7
Liabilities:
Derivatives	0.5	4.7
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	3.9	5.7
Liabilities:
Derivatives	0	2.5
Carrying Amount [Member]
Assets:
Money market fund investments	161.8	0
Deferred proceeds	214.6	119.4
Liabilities:
Long-term debt (incl. current maturities)	6,144.9	5,502.8
Carrying Amount [Member] | IPL [Member]
Assets:
Deferred proceeds	214.6	119.4
Liabilities:
Long-term debt (incl. current maturities)	2,850.5	2,552.3
Carrying Amount [Member] | WPL [Member]
Assets:
Money market fund investments	160.4	0
Liabilities:
Long-term debt (incl. current maturities)	2,181.8	1,834.9
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	21.9	28.3
Liabilities:
Derivatives	28	23.3
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	13.9	17.7
Liabilities:
Derivatives	12.2	11.2
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	8	10.6
Liabilities:
Derivatives	$ 15.8	$ 12.1

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 0.4	$ (29.4)	$ 12.2	$ (12.2)
Total net gains (losses) included in changes in net assets (realized/unrealized)		(0.1)	(0.2)	(5.7)	(10)
Transfers out of Level 3		3.9	0	3.9	0
Purchases		13.8	26.7	13.8	26.7
Sales				(0.2)	0
Settlements		(4.8)	(7.8)	(10.8)	(15.2)
Ending balance		13.2	(10.7)	13.2	(10.7)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		0	(0.1)	(2.6)	(9.7)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		0.6	(15.4)	9	(1.4)
Total net gains (losses) included in changes in net assets (realized/unrealized)		0.4	(1.6)	(2.8)	(9.2)
Transfers out of Level 3		2.5	0	2.5	0
Purchases		9.5	19.3	9.5	19.3
Sales				(0.1)	0
Settlements		(3.7)	(6.4)	(8.8)	(12.8)
Ending balance		9.3	(4.1)	9.3	(4.1)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		0.5	(1.6)	(0.9)	(9)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		(0.2)	(14)	3.2	(10.8)
Total net gains (losses) included in changes in net assets (realized/unrealized)		(0.5)	1.4	(2.9)	(0.8)
Transfers out of Level 3		1.4	0	1.4	0
Purchases		4.3	7.4	4.3	7.4
Sales				(0.1)	0
Settlements		(1.1)	(1.4)	(2)	(2.4)
Ending balance		3.9	(6.6)	3.9	(6.6)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		(0.5)	1.5	(1.7)	(0.7)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		178.3	120.9	119.4	222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)		0	0	0	0
Transfers out of Level 3		0	0	0	0
Purchases		0	0	0	0
Sales				0	0
Settlements	[1]	36.3	87.4	95.2	(13.8)
Ending balance		214.6	208.3	214.6	208.3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		0	0	0	0
Deferred Proceeds [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		178.3	120.9	119.4	222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)		0	0	0	0
Transfers out of Level 3		0	0	0	0
Purchases		0	0	0	0
Sales				0	0
Settlements	[1]	36.3	87.4	95.2	(13.8)
Ending balance		214.6	208.3	214.6	208.3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$ 0	$ 0	$ 0	$ 0
[1]	Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Measurements (Fair_3

Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 13.2	$ 0.4	$ 12.2	$ (10.7)	$ (29.4)	$ (12.2)
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	2.4		3.2
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	10.8		9
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	9.3	0.6	9	(4.1)	(15.4)	(1.4)
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	1.4		1.8
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	7.9		7.2
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3.9	$ (0.2)	3.2	$ (6.6)	$ (14)	$ (10.8)
WPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	1		1.4
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 2.9		$ 1.8

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,327
Present value abandonment obligation	37
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	773
Indemnification obligations, maximum	17
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	543
Capital Purchase Obligation [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	268
Capital Purchase Obligation [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	237
Capital Purchase Obligation [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	31
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	184	[1]
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	183	[1]
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1	[1]
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Indemnification obligations, maximum	90
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Indemnification obligations, maximum	$ 17
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	54.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	60.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	82.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	27.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	82.00%
Notice to cancel extension	30 days
[1]	Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million .

Commitments And Contingencies_3

Commitments And Contingencies (Other Purchase Commitments) (Details) - USD ($) $ in Millions		1 Months Ended	6 Months Ended
		Sep. 30, 2020	Jun. 30, 2019
Commitments and Contingencies [Line Items]
Minimum future commitments			$ 1,327
Individual commitments incurred			1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			773
Individual commitments incurred			1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			543
Individual commitments incurred			1
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]		184
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]		183
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]		1
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			925
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			460
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			465
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[2]		130
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[2]		81
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[2]		49
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[3]		88
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[3]		49
Other [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[3]		$ 28
Forecast [Member] | DAEC PPA [Member]
Commitments and Contingencies [Line Items]
Buyout payment		$ 110
[1]	Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million .
[2]	Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of June 30, 2019 regarding expected future usage, which is subject to change.
[3]	Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2019 .

Commitments And Contingencies_4

Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	$ 19
IPL [Member]
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	16
Minimum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	15
Minimum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	12
Maximum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	31
Maximum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	$ 26

Segments Of Business (Schedule

Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 790.2	$ 816.1	$ 1,777.4	$ 1,732.4
Operating income (loss)	149.8	151.2	326.6	316.9
Net income attributable to common shareowners	94.6	100.4	219.7	221.3
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	441.2	474.8	996.3	1,000.6
Operating income (loss)	74.5	77.7	148	153.3
Net income attributable to common shareowners	45	51.7	98.3	98.4
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	326.1	330.8	741.3	712.5
Operating income (loss)	67	63.4	165.1	147.4
Net income attributable to common shareowners	42	39.8	107.7	93.8
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	691.2	726.3	1,434.6	1,435
Operating income (loss)	132.9	134.8	259.3	261.5
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	392.3	422.1	812.1	827.8
Operating income (loss)	68.9	73.5	115.7	131
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	298.9	304.2	622.5	607.2
Operating income (loss)	64	61.3	143.6	130.5
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	65.2	68.6	281	254.2
Operating income (loss)	7.2	5.4	52.4	36.9
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	38.4	42.2	163	150.3
Operating income (loss)	4.2	2.5	30.5	19.4
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	26.8	26.4	118	103.9
Operating income (loss)	3	2.9	21.9	17.5
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	10.9	10.7	22	23.9
Operating income (loss)	1.4	0.9	1.4	2.3
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	10.5	10.5	21.2	22.5
Operating income (loss)	1.4	1.7	1.8	2.9
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0.4	0.2	0.8	1.4
Operating income (loss)	0	(0.8)	(0.4)	(0.6)
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	767.3	805.6	1,737.6	1,713.1
Operating income (loss)	141.5	141.1	313.1	300.7
Net income attributable to common shareowners	87	91.5	206	192.2
Non-Utility [Member] | ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	22.9	10.5	39.8	19.3
Operating income (loss)	8.3	10.1	13.5	16.2
Net income attributable to common shareowners	$ 7.6	$ 8.9	$ 13.7	$ 29.1

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
ATC [Member] | WPL Owed ATC LLC [Member] | Equity Method Investee [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 8	$ 8

Related Parties (Service Agreem

Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Administrative and General Services Billings [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 47	$ 44	$ 90	$ 85
Administrative and General Services Billings [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	35	34	68	67
Sales Credited [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	12	18	27	23
Sales Credited [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	3	8	4	9
Purchases Billed [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	74	80	158	173
Purchases Billed [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 29	$ 20	$ 59	$ 37

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Subsidiary of Common Parent [Member] - Corporate Services [Member] - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 108	$ 95
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 72	$ 71

Related Parties (Amounts Billed

Related Parties (Amounts Billed Between Parties) (Details) - ATC [Member] - Equity Method Investee [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
ATC Billings To WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 27	$ 26	$ 54	$ 53
WPL Billings To ATC [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 3	$ 3	$ 7	$ 5