Black Hills (BKH) 10-Q7 Nov 242024 Q3 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2024	Nov. 04, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-31303
Entity Registrant Name	Black Hills Corporation
Entity Incorporation, State or Country Code	SD
Entity Tax Identification Number	46-0458824
Entity Address, Address Line One	7001 Mount Rushmore Road
Entity Address, City or Town	Rapid City
Entity Address, State or Province	SD
Entity Address, Postal Zip Code	57702
City Area Code	605
Local Phone Number	721-1700
Title of 12(b) Security	Common stock of $1.00 par value
Trading Symbol	BKH
Security Exchange Name	NYSE
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		71,573,235
Entity Central Index Key	0001130464
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue:
Revenue	$ 401.6	$ 407.1	$ 1,530.6	$ 1,739.6
Operating expenses:
Fuel, purchased power and cost of natural gas sold	94.5	102.2	518.2	749.8
Operations and maintenance	145.6	125.7	420.8	412.5
Depreciation and amortization	69.3	64.9	201.8	191.2
Taxes - property and production	16.4	16.5	50	49.9
Total operating expenses	325.8	309.3	1,190.8	1,403.4
Operating income	75.8	97.8	339.8	336.2
Other income (expense):
Interest expense incurred net of amounts capitalized	(50.6)	(44.5)	(144.8)	(131.8)
Interest income	5.4	3.5	12.9	5.8
Other income (expense), net	(1.3)	(0.6)	(1.7)	(1.5)
Total other income (expense)	(46.5)	(41.6)	(133.6)	(127.5)
Income before income taxes	29.3	56.2	206.2	208.7
Income tax (expense)	(2.9)	(7.4)	(23.6)	(16)
Net income	26.4	48.8	182.6	192.7
Net income attributable to non-controlling interest	(2)	(3.4)	(7.6)	(10.2)
Net income available for common stock	$ 24.4	$ 45.4	$ 175	$ 182.5
Earnings per share of common stock:
Earnings per share, Basic (usd per share)	$ 0.35	$ 0.67	$ 2.53	$ 2.74
Earnings per share, Diluted (usd per share)	$ 0.35	$ 0.67	$ 2.52	$ 2.74
Weighted average common shares outstanding:
Basic (in shares)	70.5	67.3	69.2	66.7
Diluted (in shares)	70.6	67.4	69.3	66.7

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net income	$ 26.4	$ 48.8	$ 182.6	$ 192.7
Other comprehensive income (loss), net of tax:
Reclassification adjustments of benefit plan liability - net loss (net of tax of $0.0, $0.0, $0.0, and $(0.1), respectively)	0	0	0.1	0.1
Net unrealized gains (losses) on commodity derivatives (net of tax of $0.0, $0.1, $0.0, and $0.3, respectively)	0.1	(0.2)	(0.1)	(0.9)
Other comprehensive income, net of tax	0.7	0.4	4.2	2.7
Comprehensive income	27.1	49.2	186.8	195.4
Less: comprehensive income attributable to non-controlling interest	(2)	(3.4)	(7.6)	(10.2)
Comprehensive income available for common stock	25.1	45.8	179.2	185.2
Interest rate swaps
Other comprehensive income (loss), net of tax:
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, after tax	0.6	0.6	1.7	1.6
Commodity derivatives
Other comprehensive income (loss), net of tax:
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, after tax	$ 0	$ 0	$ 2.5	$ 1.9

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
(Tax) benefit on reclassification adjustment of benefit plan liability - net loss	$ 0	$ 0	$ 0	$ (0.1)
Interest Rate Swap
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification,Tax (Benefit)	(0.2)	(0.2)	(0.5)	(0.5)
Commodity Contract
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification,Tax (Benefit)	0	0.1	0	0.3
(Tax) benefit on net unrealized gains (losses) on commodity derivatives	$ 0	$ 0	$ (0.7)	$ (0.6)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 12.5	$ 86.6
Restricted cash and equivalents	7.1	6.4
Accounts receivable, net	205.4	350.3
Materials, supplies and fuel	155.4	160.9
Income tax receivable, net	19.9	18.5
Regulatory assets, current	156.1	175.7
Other current assets	43.1	28.2
Total current assets	599.5	826.6
Property, plant and equipment	9,383	8,917.2
Less accumulated depreciation	(1,913.4)	(1,797.9)
Total property, plant and equipment, net	7,469.6	7,119.3
Other assets:
Goodwill	1,299.5	1,299.5
Intangible assets, net	7.9	8.4
Regulatory assets, non-current	276.1	304.4
Other assets, non-current	66.1	62.2
Total other assets, non-current	1,649.6	1,674.5
TOTAL ASSETS	9,718.7	9,620.4
Current liabilities:
Accounts payable	136.3	186.4
Accrued liabilities	291.7	293.3
Derivative liabilities, current	4.5	6.5
Regulatory liabilities, current	86.2	98.9
Notes payable	17.5	0
Current maturities of long-term debt	0	600
Total current liabilities	536.2	1,185.1
Long-term debt, net of current maturities	4,248.8	3,801.2
Deferred credits and other liabilities:
Deferred income tax liabilities, net	603.3	548
Regulatory liabilities, non-current	470.8	467.7
Benefit plan liabilities	122.9	123.9
Other deferred credits and other liabilities	204.5	188.7
Total deferred credits and other liabilities	1,401.5	1,328.3
Commitments, contingencies and guarantees (Note 3)
Equity:
Common stock $1 par value; 100,000,000 shares authorized; issued 71,676,746 and 68,265,042 shares, respectively	71.7	68.3
Additional paid-in capital	2,193.9	2,007.7
Retained earnings	1,197.5	1,158.2
Treasury stock, at cost - 101,471 and 68,073 shares, respectively	(5.9)	(4.1)
Accumulated other comprehensive income (loss)	(10.6)	(14.8)
Total stockholders’ equity	3,446.6	3,215.3
Non-controlling interest	85.6	90.5
Total equity	3,532.2	3,305.8
TOTAL LIABILITIES AND TOTAL EQUITY	$ 9,718.7	$ 9,620.4

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Common stock, par value (usd per share)	$ 1	$ 1
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares, issued	71,676,746	68,265,042
Treasury stock, shares	101,471	68,073

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Operating activities:
Net income	$ 182.6	$ 192.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	201.8	191.2
Deferred financing cost amortization	8.2	6.9
Stock compensation	8.2	4.6
Deferred income taxes	39.6	16.1
Employee benefit plans	8.9	7.9
Other adjustments, net	(1.8)	(6.1)
Change in certain operating assets and liabilities:
Materials, supplies and fuel	10.9	43.5
Accounts receivable and other current assets	123.9	302.8
Accounts payable and other current liabilities	(61.8)	(186.5)
Regulatory assets	61.6	199.1
Other operating activities, net	(16)	(16.2)
Net cash provided by operating activities	566.1	756
Investing activities:
Property, plant and equipment additions	(530.5)	(421.8)
Other investing activities	(1.5)	18
Net cash (used in) investing activities	(532)	(403.8)
Financing activities:
Dividends paid on common stock	(135.8)	(125.4)
Common stock issued	181.6	107.4
Net borrowings (payments) of Revolving Credit Facility and CP Program	17.5	(535.6)
Long-term debt - issuance	450	800
Long-term debt - repayments	(600)	0
Distributions to non-controlling interests	(12.5)	(12.9)
Other financing activities	(8.3)	(12.2)
Net cash provided by (used in) financing activities	(107.5)	221.3
Net change in cash, restricted cash and cash equivalents	(73.4)	573.5
Cash, restricted cash and cash equivalents beginning of period	93	27
Cash, restricted cash and cash equivalents end of period	19.6	600.5
Supplemental cash flow information:
Interest (net of amounts capitalized)	(122.5)	(108.8)
Income taxes, net of transferred tax credits (Note 11)	14.6	0.1
Accrued property, plant and equipment purchases at September 30,	$ 64	$ 53

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2022		66,140,396	36,726
Beginning balance at Dec. 31, 2022	$ 3,089.9	$ 66.1	$ (2.4)	$ 1,882.7	$ 1,064.1	$ (15.6)	$ 95
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	117.4				114.1		3.3
Other comprehensive income, net of tax	1.2					1.2
Dividends on common stock	(41.4)				(41.4)
Share-based compensation (in shares)		84,735	4,388
Share-based compensation	1.7	$ 0.1	$ (0.3)	1.9
Issuance of common stock (in shares)		445,578
Issuance of common stock	27.7	$ 0.5		27.2
Issuance costs	(0.3)			(0.3)
Distributions to non-controlling interest	(4.5)						(4.5)
Ending balance (in shares) at Mar. 31, 2023		66,670,709	41,114
Ending balance at Mar. 31, 2023	3,191.7	$ 66.7	$ (2.7)	1,911.5	1,136.8	(14.4)	93.8
Beginning balance (in shares) at Dec. 31, 2022		66,140,396	36,726
Beginning balance at Dec. 31, 2022	3,089.9	$ 66.1	$ (2.4)	1,882.7	1,064.1	(15.6)	95
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	192.7
Other comprehensive income, net of tax	2.7
Ending balance (in shares) at Sep. 30, 2023		68,046,262	54,428
Ending balance at Sep. 30, 2023	3,259.6	$ 68	$ (3.5)	1,994.4	1,121.3	(12.9)	92.3
Beginning balance (in shares) at Mar. 31, 2023		66,670,709	41,114
Beginning balance at Mar. 31, 2023	3,191.7	$ 66.7	$ (2.7)	1,911.5	1,136.8	(14.4)	93.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26.6				23.1		3.5
Other comprehensive income, net of tax	1.1					1.1
Dividends on common stock	(41.7)				(41.7)
Share-based compensation (in shares)		8,492	7,509
Share-based compensation	2.4		$ (0.5)	2.9
Issuance of common stock (in shares)		436,202
Issuance of common stock	27.6	$ 0.4		27.2
Issuance costs	(0.4)			(0.4)
Distributions to non-controlling interest	(4.5)						(4.5)
Ending balance (in shares) at Jun. 30, 2023		67,115,403	48,623
Ending balance at Jun. 30, 2023	3,202.8	$ 67.1	$ (3.2)	1,941.2	1,118.2	(13.3)	92.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	48.8				45.4		3.4
Other comprehensive income, net of tax	0.4					0.4
Dividends on common stock	(42.3)				(42.3)
Share-based compensation (in shares)		15	5,805
Share-based compensation	1.2		$ (0.3)	1.5
Issuance of common stock (in shares)		930,844
Issuance of common stock	53.3	$ 0.9		52.4
Issuance costs	(0.7)			(0.7)
Distributions to non-controlling interest	(3.9)						(3.9)
Ending balance (in shares) at Sep. 30, 2023		68,046,262	54,428
Ending balance at Sep. 30, 2023	3,259.6	$ 68	$ (3.5)	1,994.4	1,121.3	(12.9)	92.3
Beginning balance (in shares) at Dec. 31, 2023		68,265,042	68,073
Beginning balance at Dec. 31, 2023	3,305.8	$ 68.3	$ (4.1)	2,007.7	1,158.2	(14.8)	90.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	131.6				127.9		3.7
Other comprehensive income, net of tax	2.5					2.5
Dividends on common stock	(44.4)				(44.4)
Share-based compensation (in shares)		104,181	14,270
Share-based compensation	1.4	$ 0.1	$ (0.6)	1.9
Issuance of common stock (in shares)		600,355
Issuance of common stock	31.5	$ 0.6		30.9
Issuance costs	(0.3)			(0.3)
Distributions to non-controlling interest	(5.6)						(5.6)
Ending balance (in shares) at Mar. 31, 2024		68,969,578	82,343
Ending balance at Mar. 31, 2024	3,422.5	$ 69	$ (4.7)	2,040.2	1,241.7	(12.3)	88.6
Beginning balance (in shares) at Dec. 31, 2023		68,265,042	68,073
Beginning balance at Dec. 31, 2023	3,305.8	$ 68.3	$ (4.1)	2,007.7	1,158.2	(14.8)	90.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	182.6
Other comprehensive income, net of tax	4.2
Ending balance (in shares) at Sep. 30, 2024		71,676,746	101,471
Ending balance at Sep. 30, 2024	3,532.2	$ 71.7	$ (5.9)	2,193.9	1,197.5	(10.6)	85.6
Beginning balance (in shares) at Mar. 31, 2024		68,969,578	82,343
Beginning balance at Mar. 31, 2024	3,422.5	$ 69	$ (4.7)	2,040.2	1,241.7	(12.3)	88.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24.7				22.8		1.9
Other comprehensive income, net of tax	1					1
Dividends on common stock	(44.9)				(44.9)
Share-based compensation (in shares)		9,623	817
Share-based compensation	2.7		$ (0.2)	2.9
Issuance of common stock (in shares)		768,019
Issuance of common stock	42.2	$ 0.7		41.5
Issuance costs	(0.4)			(0.4)
Distributions to non-controlling interest	(4.4)						(4.4)
Ending balance (in shares) at Jun. 30, 2024		69,747,220	83,160
Ending balance at Jun. 30, 2024	3,443.4	$ 69.7	$ (4.9)	2,084.2	1,219.6	(11.3)	86.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26.4				24.4		2
Other comprehensive income, net of tax	0.7					0.7
Dividends on common stock	(46.5)				(46.5)
Share-based compensation (in shares)		10	18,311
Share-based compensation	2.1		$ (1)	3.1
Issuance of common stock (in shares)		1,929,516
Issuance of common stock	109.7	$ 2		107.7
Issuance costs	(1.1)			(1.1)
Distributions to non-controlling interest	(2.5)						(2.5)
Ending balance (in shares) at Sep. 30, 2024		71,676,746	101,471
Ending balance at Sep. 30, 2024	$ 3,532.2	$ 71.7	$ (5.9)	$ 2,193.9	$ 1,197.5	$ (10.6)	$ 85.6

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Statement of Stockholders' Equity [Abstract]
Dividends on common stock (usd per share)	$ 0.65	$ 0.65	$ 0.65	$ 0.625	$ 0.625	$ 0.625

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 24.4	$ 45.4	$ 175	$ 182.5

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10b5-1 Arrangement Modified	false
Non-Rule 10b5-1 Arrangement Modified	false

Management's Statement

Management's Statement	9 Months Ended
Management's Statement	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Statement	(1) Manage ment’s Statement The unaudited Consolidated Financial Statements included herein have been prepared by Black Hills Corporation (together with our subsidiaries the “Company”, “us”, “we”, or “our”), pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to such rules and regulations; however, we believe that the footnotes adequately disclose the information presented. These Consolidated Financial Statements should be read in conjunction with the consolidated financial statements and the notes included in our 2023 Annual Report on Form 10-K. Use of Estimates and Basis of Presentation The information furnished in the accompanying Consolidated Financial Statements reflects certain estimates required and all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the September 30, 2024, December 31, 2023, and September 30, 2023 , financial information. Certain lines of business in which we operate are highly seasonal and our interim results of operations are not necessarily indicative of the results of operations to be expected for an entire year. Recently Issued Accounting Standards Improvements to Reportable Segment Disclosures, ASU 2023-07 In November 2023, the FASB issued ASU 2023-07, Improvements to Reportable Segment Disclosures , which expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly reviewed by the CODM and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. ASU 2023-07 also allows, in addition to the measure that is most consistent with GAAP, the disclosure of additional measures of segment profit or loss that are used by the CODM in assessing segment performance and deciding how to allocate resources. ASU 2023-07 is effective for our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, and subsequent interim periods, with early adoption permitted. We do not expect ASU 2023-07 to have an impact on our financial position, results of operations and cash flows; however, are currently evaluating the impact on our consolidated financial statement disclosures. Improvements to Income Tax Disclosures, ASU 2023-09 In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures , which expands public entities’ annual disclosures by requiring disclosure of tax rate reconciliation amounts and percentages for specific categories, income taxes paid disaggregated by federal and state taxes, and income tax expense disaggregated by federal and state taxes jurisdiction. ASU 2023-09 is effective for our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, with early adoption permitted. We do not expect ASU 2023-09 to have an impact on our financial position, results of operations and cash flows; however, are currently evaluating the impact on our consolidated financial statement disclosures.

Regulatory Matters

Regulatory Matters	9 Months Ended
Regulatory Matters	Sep. 30, 2024
Regulated Operations [Abstract]
Regulatory Matters	(2) Regul atory Matters We had the following regulatory assets and liabilities: As of As of September 30, 2024 December 31, 2023 (in millions) Regulatory assets Winter Storm Uri $ 123.4 $ 199.6 Deferred energy and fuel cost adjustments 61.1 55.1 Deferred gas cost adjustments 17.2 4.1 Gas price derivatives 3.2 5.1 Deferred taxes on AFUDC 7.7 7.1 Employee benefit plans and related deferred taxes 86.1 89.3 Environmental 10.6 2.9 Loss on reacquired debt 16.1 17.4 Deferred taxes on flow through accounting 80.9 74.7 Decommissioning costs 2.4 2.4 Other regulatory assets 23.5 22.4 Total regulatory assets 432.2 480.1 Less current regulatory assets ( 156.1 ) ( 175.7 ) Regulatory assets, non-current $ 276.1 $ 304.4 Regulatory liabilities Deferred energy and gas costs $ 82.6 $ 88.9 Employee benefit plan costs and related deferred taxes 34.6 36.2 Cost of removal 193.2 181.9 Excess deferred income taxes 240.5 247.1 Other regulatory liabilities 6.1 12.5 Total regulatory liabilities 557.0 566.6 Less current regulatory liabilities ( 86.2 ) ( 98.9 ) Regulatory liabilities, non-current $ 470.8 $ 467.7 Regulatory Activity Arkansas Gas On December 4, 2023, Arkansas Gas filed a rate review with the APSC seeking recovery of significant infrastructure investments in its 7,200 -mile natural gas pipeline system. On October 1, 2024, Arkansas Gas received final approval for a settlement agreement for a general rate increase which is expected to generate $ 25.4 million of new annual revenue and shift $ 3.7 million of rider revenue to base rates. The approval allows a capital structure of 46 % equity and 54 % debt and a return on equity of 9.9 %. New rates were effective October 14, 2024. Colorado Electric On June 14, 2024, Colorado Electric filed a rate review with the CPUC seeking recovery of significant infrastructure investments in its 3,200 -mile electric distribution and 600 -mile electric transmission systems. The rate review requests $ 36.7 million in new annual revenue with a capital structure of 53 % equity and 47 % debt and a return on equity of 10.5 %. The request seeks to finalize rates in the first quarter of 2025. Colorado Gas On May 9, 2023, Colorado Gas filed a rate review with the CPUC seeking recovery of significant infrastructure investments in its 10,000 -mile natural gas pipeline system. In March 2024, Colorado Gas received final approval for a settlement agreement for a general rate increase which is expected to generate $ 20.2 million of new annual revenue with a capital structure of 51 % equity and 49 % debt and a return on equity of 9.3 %. Final rates were enacted on May 1, 2024, and replaced interim rates effective February 13, 2024. Iowa Gas On May 1, 2024, Iowa Gas filed a rate review with the IUC seeking recovery of significant infrastructure investments in its 5,000 -mile natural gas pipeline system. On October 15, 2024, Iowa Gas reached a settlement agreement with the Iowa Office of Consumer Advocate for a general rate increase, which is subject to IUC approval. T he settlement is expected to generate $ 15.0 million of new annual revenue based on a weighted average cost of capital of 7.2 %. If approved, new rates will be effective in the first quarter of 2025 and will replace interim rates effective May 11, 2024. Wyoming Gas On May 18, 2023, Wyoming Gas filed a rate review with the WPSC seeking recovery of significant infrastructure investments in its 6,400 -mile natural gas pipeline system. On January 17, 2024, the WPSC approved a settlement agreement for a general rate increase which is expected to generate $ 13.9 million in new annual revenue with a capital structure of 51 % equity and 49 % debt and a return on equity of 9.9 %. New rates were effective February 1, 2024. The agreement also included approval of a four-year extension of the Wyoming Integrity Rider.

Commitment, Contingencies And G

Commitment, Contingencies And Guarantees	9 Months Ended
Commitment, Contingencies And Guarantees	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Guarantees	(3) Comm itments, Contingencies and Guarantees There have been no significant changes to commitments, contingencies and guarantees from those previously disclosed in Note 3 of our Notes to the Consolidated Financial Statements in our 2023 Annual Report on Form 10-K except as described below. Manufactured Gas Plant In 2008, we acquired whole and partial liabilities for former manufactured gas plant sites in Nebraska and Iowa, which were previously used to convert coal to natural gas. The acquisition provided for an insurance recovery, now valued at $ 1.5 million recorded in Other assets, non-current on our Consolidated Balance Sheets, which will be used to help offset remediation costs. During the nine months ended September 30, 2024 , we increased our Iowa manufactured gas plant site remediation cost estimate by $ 7.4 million based on recent site investigations and remediation work completed, which resulted in a corresponding increase in our Accrued liabilities and Regulatory assets. As of September 30, 2024 , we had an Accrued liability of $ 11.5 million and a Regulatory asset of $ 10.6 million on our Consolidated Balance Sheets for the remediation of the manufactured gas plant site in Iowa. The remediation cost estimate could change materially due to results of further investigations, actions of environmental agencies or the financial viability of other responsible parties.

Revenue

Revenue	9 Months Ended
Revenue	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue	(4) Rev enue The following tables depict the disaggregation of revenue, including intercompany revenue, from contracts with customers by customer type and timing of revenue recognition for each of the reportable segments for the three and nine months ended September 30, 2024, and 2023. Sales tax and other similar taxes are excluded from revenues. Three Months Ended September 30, 2024 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 195.5 $ 117.4 $ - $ 312.9 Transportation - 43.2 ( 0.2 ) 43.0 Wholesale 6.2 - - 6.2 Market - off-system sales 10.8 - - 10.8 Transmission/Other 19.1 10.9 ( 4.3 ) 25.7 Revenue from contracts with customers $ 231.6 $ 171.5 $ ( 4.5 ) $ 398.6 Other revenues 0.9 2.1 - 3.0 Total revenues $ 232.5 $ 173.6 $ ( 4.5 ) $ 401.6 Timing of revenue recognition: Services transferred at a point in time $ 9.3 $ - $ - $ 9.3 Services transferred over time 222.3 171.5 ( 4.5 ) 389.3 Revenue from contracts with customers $ 231.6 $ 171.5 $ ( 4.5 ) $ 398.6 Three Months Ended September 30, 2023 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 191.0 $ 120.8 $ - $ 311.8 Transportation - 42.7 ( 0.1 ) 42.6 Wholesale 9.4 - - 9.4 Market - off-system sales 13.0 - - 13.0 Transmission/Other 18.1 9.6 ( 4.4 ) 23.3 Revenue from contracts with customers $ 231.5 $ 173.1 $ ( 4.5 ) $ 400.1 Other revenues 5.8 1.2 - 7.0 Total revenues $ 237.3 $ 174.3 $ ( 4.5 ) $ 407.1 Timing of revenue recognition: Services transferred at a point in time $ 7.8 $ - $ - $ 7.8 Services transferred over time 223.7 173.1 ( 4.5 ) 392.3 Revenue from contracts with customers $ 231.5 $ 173.1 $ ( 4.5 ) $ 400.1 Nine Months Ended September 30, 2024 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 555.1 $ 707.7 $ - $ 1,262.8 Transportation - 130.8 ( 0.3 ) 130.5 Wholesale 21.2 - - 21.2 Market - off-system sales 22.8 0.1 - 22.9 Transmission/Other 56.6 32.1 ( 13.1 ) 75.6 Revenue from contracts with customers $ 655.7 $ 870.7 $ ( 13.4 ) $ 1,513.0 Other revenues 4.1 13.5 - 17.6 Total revenues $ 659.8 $ 884.2 $ ( 13.4 ) $ 1,530.6 Timing of revenue recognition: Services transferred at a point in time $ 25.9 $ - $ - $ 25.9 Services transferred over time 629.8 870.7 ( 13.4 ) 1,487.1 Revenue from contracts with customers $ 655.7 $ 870.7 $ ( 13.4 ) $ 1,513.0 Nine Months Ended September 30, 2023 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 522.3 $ 931.1 $ - $ 1,453.4 Transportation - 131.4 ( 0.3 ) 131.1 Wholesale 24.6 - - 24.6 Market - off-system sales 37.5 0.4 - 37.9 Transmission/Other 54.7 28.8 ( 13.1 ) 70.4 Revenue from contracts with customers $ 639.1 $ 1,091.7 $ ( 13.4 ) $ 1,717.4 Other revenues 10.0 12.2 - 22.2 Total revenues $ 649.1 $ 1,103.9 $ ( 13.4 ) $ 1,739.6 Timing of revenue recognition: Services transferred at a point in time $ 24.3 $ - $ - $ 24.3 Services transferred over time 614.8 1,091.7 ( 13.4 ) 1,693.1 Revenue from contracts with customers $ 639.1 $ 1,091.7 $ ( 13.4 ) $ 1,717.4

Financing

Financing	9 Months Ended
Financing	Sep. 30, 2024
Debt Disclosure [Abstract]
Financing	(5) Fin ancing Short-term Debt Revolving Credit Facility and CP Program On May 31, 2024, we amended and restated our corporate Revolving Credit Facility, maintaining total commitments of $ 750 million and extending the term through May 31, 2029, with two one-year extension options (subject to consent from lenders). This facility is similar to the former revolving credit facility, which includes an accordion feature that allows us, with the consent of the administrative agent, the issuing agents and each bank increasing or providing a new commitment, to increase total commitments up to $ 1.0 billion. Borrowings continue to be available under a base rate or various SOFR options. Based on our current credit ratings, the margins for base rate borrowings, SOFR borrowings and letters of credit will be 0.125 %, 1.125 %, and 1.125 %, respectively, and a 0.175 % commitment fee will be charged on unused amounts. Our Revolving Credit Facility and CP Program, which are classified as Notes payable on the Consolidated Balance Sheets, had the following borrowings, outstanding letters of credit, and available capacity as of: September 30, 2024 December 31, 2023 (dollars in millions) Amount outstanding $ 17.5 $ - Letters of credit (a) $ 3.5 $ 3.7 Available capacity $ 729.0 $ 746.3 Weighted average interest rates 4.93 % N/A (a) Letters of credit are off-balance sheet commitments that reduce the borrowing capacity available on our corporate Revolving Credit Facility . Revolving Credit Facility and CP Program borrowing activity was as follows: Nine Months Ended September 30, 2024 2023 (dollars in millions) Maximum amount outstanding (based on daily outstanding balances) $ 25.8 $ 548.7 Average amount outstanding (based on daily outstanding balances) $ 0.6 $ 109.2 Weighted average interest rates 5.15 % 4.91 % Long-term Debt On May 16, 2024, we completed a public debt offering of $ 450 million, 6.00 % senior unsecured notes due January 15, 2035. Proceeds from the offering, which were net of $ 5.2 million of deferred financing costs, along with available cash and short-term borrowings under our existing facilities were used to repay all $ 600 million principal amount outstanding of our 1.04 % senior unsecured notes on their August 23, 2024, maturity date and for other general corporate purposes. Financial Covenants Revolving Credit Facility We were in compliance with all of our Revolving Credit Facility covenants as of September 30, 2024 . We are required to maintain a Consolidated Indebtedness to Capitalization Ratio not to exceed 0.65 to 1.00. Subject to applicable cure periods, a violation of this covenant would constitute an event of default that entitles the lenders to terminate their remaining commitments and accelerate all principal and interest outstanding. As of September 30, 2024, our Consolidated Indebtedness to Capitalization Ratio was 0.55 to 1.00. Wyoming Electric Wyoming Electric was in compliance with all covenants within its financing agreements as of September 30, 2024 . Wyoming Electric is required to maintain a debt to capitalization ratio of no more than 0.60 to 1.00. As of September 30, 2024 , Wyoming Electric's debt to capitalization ratio was 0.52 to 1.00. Equity At-the-Market Equity Offering Program ATM activity was as follows: Three Months Ended September 30, Nine Months Ended September 30, 2024 (a) 2023 2024 (a) 2023 August 4, 2020 ATM Program (in millions, except Average price per share amounts) Proceeds, (net of issuance costs of $ 0.0 , $ 0.0 , $ 0.0 , and $( 0.5 ), respectively) $ - $ - $ - $ 48.5 Number of shares issued - - - 0.8 June 16, 2023 ATM Program Proceeds, (net of issuance costs of $( 1.1 ), $( 0.5 ), $( 1.8 ), and $( 0.6 ), respectively) $ 108.6 $ 52.8 $ 181.6 $ 59.2 Number of shares issued 1.9 0.9 3.3 1.0 Total activity under both ATM Programs Proceeds, (net of issuance costs of $( 1.1 ), $( 0.5 ), $( 1.8 ), and $( 1.1 ), respectively) $ 108.6 $ 52.8 $ 181.6 $ 107.7 Number of shares issued 1.9 0.9 3.3 1.8 Average price per share $ 56.84 $ 57.33 $ 55.63 $ 60.02 (a) In August 2024, we executed a block trade, which completed our planned equity issuances for 2024.

Earnings Per Share

Earnings Per Share	9 Months Ended
Earnings Per Share	Sep. 30, 2024
Earnings Per Share [Abstract]
Earnings Per Share	(6) Earning s Per Share A reconciliation of share amounts used to compute earnings per share in the accompanying Consolidated Statements of Income was as follows: Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 (in millions, except per share amounts) Net income available for common stock $ 24.4 $ 45.4 $ 175.0 $ 182.5 Weighted average shares - basic 70.5 67.3 69.2 66.7 Dilutive effect of equity compensation 0.1 0.1 0.1 - Weighted average shares - diluted 70.6 67.4 69.3 66.7 Net income available for common stock, per share - Diluted $ 0.35 $ 0.67 $ 2.52 $ 2.74 The following securities were excluded from the diluted earnings per share computation because of their anti-dilutive nature: Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 (in millions of shares) Equity compensation - 0.1 - - Restricted stock - - - - Anti-dilutive shares excluded from computation of earnings per share - 0.1 - -

Risk Management And Derivatives

Risk Management And Derivatives	9 Months Ended
Risk Management And Derivatives	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Risk Management And Derivatives	(7) Risk Mana gement and Derivatives Market and Credit Risk Disclosures Our activities in the energy industry expose us to a number of risks in the normal operations of our businesses. Depending on the activity, we are exposed to varying degrees of market risk and credit risk. Market Risk Market risk is the potential loss that may occur as a result of an adverse change in market price, rate or supply. We are exposed but not limited to, the following market risks: • Commodity price risk associated with our retail natural gas and wholesale electric power marketing activities and our fuel procurement for several of our gas-fired generation assets, which include market fluctuations due to unpredictable factors such as weather, geopolitical events, pandemics, market speculation, recession, inflation, pipeline constraints, and other factors that may impact natural gas and electric supply and demand; and • Interest rate risk associated with future debt, including reduced access to liquidity during periods of extreme capital markets volatility. Credit Risk Credit risk is the risk of financial loss resulting from non-performance of contractual obligations by a counterparty. We attempt to mitigate our credit exposure by conducting business primarily with high credit quality entities, setting tenor and credit limits commensurate with counterparty financial strength, obtaining master netting agreements, and mitigating credit exposure with less creditworthy counterparties through parental guarantees, cash collateral requirements, letters of credit, and other security agreements. We perform periodic credit evaluations of our customers and adjust credit limits based upon payment history and the customers’ current creditworthiness, as determined by review of their current credit information. We maintain a provision for estimated credit losses based upon historical experience, changes in current market conditions, expected losses, and any specific customer collection issue that is identified. Derivatives and Hedging Activity Our derivative and hedging activities included in the accompanying Consolidated Balance Sheets, Consolidated Statements of Income, and Consolidated Statements of Comprehensive Income are detailed below and in Note 8 . The operations of our Utilities, including natural gas sold by our Gas Utilities and natural gas used by our Electric Utilities’ generation plants or those plants under PPAs where our Electric Utilities must provide the generation fuel (tolling agreements), expose our utility customers to natural gas price volatility. Therefore, as allowed or required by state utility commissions, we enter into commission approved hedging programs utilizing natural gas futures, options, over-the-counter swaps and basis swaps to reduce our customers’ underlying exposure to these fluctuations. These transactions are considered derivatives, and in accordance with accounting standards for derivatives and hedging, mark-to-market adjustments are recorded as Derivative assets or Derivative liabilities on the accompanying Consolidated Balance Sheets, net of balance sheet offsetting as permitted by GAAP. For our regulated Utilities’ hedging plans, unrealized and realized gains and losses, as well as option premiums and commissions on these transactions, are recorded as Regulatory assets or Regulatory liabilities in the accompanying Consolidated Balance Sheets in accordance with the state regulatory commission guidelines. When the related costs are recovered through our rates, the hedging activity is recognized in the Consolidated Statements of Income. To support our Choice Gas Program customers, we buy, sell, and deliver natural gas at competitive prices by managing commodity price risk. As a result of these activities, this area of our business is exposed to risks associated with changes in the market price of natural gas. We manage our exposure to such risks using over-the-counter and exchange traded options and swaps with counterparties in anticipation of forecasted purchases and sales during time frames ranging from October 2024 through August 2026. A portion of our over-the-counter swaps have been designated as cash flow hedges to mitigate the commodity price risk associated with deliveries under fixed price forward contracts to deliver gas to our Choice Gas Program customers. The gain or loss on these designated derivatives is reported in AOCI in the accompanying Consolidated Balance Sheets and reclassified into earnings in the same period that the underlying hedged item is recognized in earnings. Effectiveness of our hedging position is evaluated at least quarterly. The contract or notional amounts and terms of the electric and natural gas derivative commodity instruments held at our Utilities are composed of both long and short positions. We had the following net long and (short) positions as of: September 30, 2024 December 31, 2023 Notional Amounts (MMBtus) Maximum Term (months) (a) Notional Amounts (MMBtus) Maximum Term (months) (a) Natural gas futures purchased 1,800,000 6 650,000 3 Natural gas options purchased, net 7,680,000 6 2,850,000 3 Natural gas basis swaps purchased 1,800,000 6 1,050,000 3 Natural gas over-the-counter swaps, net (b) 4,890,000 22 3,890,000 21 Natural gas physical contracts, net (c) 32,240,665 6 12,582,415 10 (a) Term reflects the maximum forward period hedged. (b) As of September 30, 2024 , 2,276,000 MMBtus of natural gas over-the-counter swaps purchases were designated as cash flow hedges. (c) Volumes exclude derivative contracts that qualify for the normal purchases and normal sales exception permitted by GAAP. We have certain derivative contracts which contain credit provisions. These credit provisions may require the Company to post collateral when credit exposure to the Company is in excess of a negotiated line of unsecured credit. At September 30, 2024, the Company post ed $ 0.5 million re lated to such provisions, which is included in Other current assets on the Consolidated Balance Sheets. Derivatives by Balance Sheet Classification The following table presents the fair value and balance sheet classification of our derivative instruments as of: Balance Sheet Location September 30, December 31, (in millions) Derivatives designated as hedges: Liability derivative instruments: Current commodity derivatives Derivative liabilities, current $ ( 0.6 ) $ ( 2.7 ) Noncurrent commodity derivatives Other assets, non-current - ( 0.2 ) Total derivatives designated as hedges $ ( 0.6 ) $ ( 2.9 ) Derivatives not designated as hedges: Liability derivative instruments: Current commodity derivatives Derivative liabilities, current $ ( 3.9 ) $ ( 3.8 ) Noncurrent commodity derivatives Other deferred credits and other liabilities ( 0.1 ) ( 0.1 ) Total derivatives not designated as hedges $ ( 4.0 ) $ ( 3.9 ) Derivatives Designated as Hedge Instruments The impact of cash flow hedges on our Consolidated Statements of Comprehensive Income and Consolidated Statements of Income are presented below for the three and nine months ended September 30, 2024, and 2023. Note that this presentation does not reflect the gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended Three Months Ended 2024 2023 2024 2023 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in OCI Income Statement Location Amount of Gain/(Loss) Reclassified from AOCI into Income (in millions) (in millions) Interest rate swaps $ 0.8 $ 0.7 Interest expense $ ( 0.8 ) $ ( 0.7 ) Commodity derivatives 0.1 ( 0.2 ) Fuel, purchased power, and cost of natural gas sold - - Total $ 0.9 $ 0.5 $ ( 0.8 ) $ ( 0.7 ) Nine Months Ended Nine Months Ended 2024 2023 2024 2023 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in OCI Income Statement Location Amount of Gain/(Loss) Reclassified from AOCI into Income (in millions) (in millions) Interest rate swaps $ 2.2 $ 2.1 I nterest expense $ ( 2.2 ) $ ( 2.1 ) Commodity derivatives 3.1 1.3 Fuel, purchased power, and cost of natural gas sold ( 3.2 ) ( 2.5 ) Total $ 5.3 $ 3.4 $ ( 5.4 ) $ ( 4.6 ) As of September 30, 2024, $ 2.9 million o f net losses related to our interest rate swaps and commodity derivatives are expected to be reclassified from AOCI into earnings within the next 12 months. As market prices fluctuate, estimated and actual realized gains or losses will change during future periods. Derivatives Not Designated as Hedge Instruments The following table summarizes the impacts of derivative instruments not designated as hedge instruments on our Consolidated Statements of Income for the three and nine months ended September 30, 2024, and 2023. Note that this presentation does not reflect the expected gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended September 30, 2024 2023 Derivatives Not Designated as Hedging Instruments Location of Gain/(Loss) on Derivatives Recognized in Income Amount of Gain/(Loss) on Derivatives Recognized in Income (in millions) Commodity derivatives Fuel, purchased power, and cost of natural gas sold $ ( 0.3 ) $ 0.3 $ ( 0.3 ) $ 0.3 Nine Months Ended September 30, 2024 2023 Derivatives Not Designated as Hedging Instruments Location of Gain/(Loss) on Derivatives Recognized in Income Amount of Gain/(Loss) on Derivatives Recognized in Income (in millions) Commodity derivatives Fuel, purchased power, and cost of natural gas sold $ 0.4 $ ( 2.4 ) $ 0.4 $ ( 2.4 ) As discussed above, financial instruments used in our regulated Gas Utilities are not designated as cash flow hedges. However, there is no earnings impact because the unrealized gains and losses arising from the use of these financial instruments are recorded as Regulatory assets or Regulatory liabilities. We had $ 3.2 million in net unrealized losses i ncluded in our Regulatory asset accounts related to these financial instruments in our Gas Utilities as of September 30, 2024, and the amount was $ 5.1 million as of December 31, 2023 .

Fair Value Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	(8) Fair Value Measurements We use the following fair value hierarchy for determining inputs for our financial instruments. Our assets and liabilities for financial instruments are classified and disclosed in one of the following fair value categories: Level 1 — Unadjusted quoted prices available in active markets that are accessible at the measurement date for identical unrestricted assets or liabilities. Level 1 instruments primarily consist of highly liquid and actively traded financial instruments with quoted pricing information on an ongoing basis. Level 2 — Pricing inputs include quoted prices for identical or similar assets and liabilities in active markets other than quoted prices in Level 1, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability, and inputs that are derived principally from, or corroborated by, observable market data by correlation or other means. Level 3 — Pricing inputs are generally less observable from objective sources. These inputs reflect management’s best estimate of fair value using its own assumptions about the assumptions a market participant would use in pricing the asset or liability. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the placement within the fair value hierarchy levels. We record transfers, if necessary, between levels at the end of the reporting period for all of our financial instruments. Transfers into Level 3, if any, occur when significant inputs used to value the derivative instruments become less observable, such as a significant decrease in the frequency and volume in which the instrument is traded, negatively impacting the availability of observable pricing inputs. Transfers out of Level 3, if any, occur when the significant inputs become more observable, such as when the time between the valuation date and the delivery date of a transaction becomes shorter, positively impacting the availability of observable pricing inputs. Recurring Fair Value Measurements Derivatives The commodity contracts for our Utilities segments are valued using the market approach and include forward strip pricing at liquid delivery points, exchange-traded futures, options, basis swaps, and over-the-counter swaps and options (Level 2) for wholesale electric energy and natural gas contracts. For exchange-traded futures, options, and basis swap assets and liabilities, fair value was derived using broker quotes validated by the exchange settlement pricing for the applicable contract. For over-the-counter instruments, the fair value is obtained by utilizing a nationally recognized service that obtains observable inputs to compute the fair value, which we validate by comparing our valuation with the counterparty. The fair value of these swaps includes a credit valuation adjustment based on the credit spreads of the counterparties when we are in an unrealized gain position or on our own credit spread when we are in an unrealized loss position. For additional information, see Note 1 of our Notes to the Consolidated Financial Statements in our 2023 Annual Report on Form 10-K. The following tables set forth, by level within the fair value hierarchy, our gross assets and gross liabilities and related offsetting as permitted by GAAP that were accounted for at fair value on a recurring basis for derivative instruments. As of September 30, 2024 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting (a) Total (in millions) Assets: Commodity derivatives - Gas Utilities $ - $ 5.6 $ - $ ( 5.6 ) $ - Total $ - $ 5.6 $ - $ ( 5.6 ) $ - Liabilities: Commodity derivatives - Gas Utilities $ - $ 5.7 $ - $ ( 1.1 ) $ 4.6 Total $ - $ 5.7 $ - $ ( 1.1 ) $ 4.6 (a) As of September 30, 2024, $ 5.6 million of our commodity derivative assets and $ 1.1 million of our commodity derivative liabilities, as well as related gross collateral amounts, were subject to master netting agreements. As of December 31, 2023 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting (a) Total (in millions) Assets: Commodity derivatives - Gas Utilities $ - $ 1.9 $ - $ ( 1.9 ) $ - Total $ - $ 1.9 $ - $ ( 1.9 ) $ - Liabilities: Commodity derivatives - Gas Utilities $ - $ 10.1 $ - $ ( 3.3 ) $ 6.8 Total $ - $ 10.1 $ - $ ( 3.3 ) $ 6.8 (a) As of December 31, 2023 , $ 1.9 million of our commodity derivative assets and $ 3.3 million of our commodity derivative liabilities, as well as related gross collateral amounts, were subject to master netting agreements. Pension and Postretirement Plan Assets Fair value measurements also apply to the valuation of our pension and postretirement plan assets. Current accounting guidance requires employers to annually disclose information about the fair value measurements of their assets of a defined benefit pension or other postretirement plan. The fair value of these assets is presented in Note 13 to the Consolidated Financial Statements included in our 2023 Annual Report on Form 10-K. Other Fair Value Measures The carrying amount of cash and cash equivalents, restricted cash and equivalents, and short-term borrowings approximates fair value due to their liquid or short-term nature. Cash, cash equivalents, and restricted cash are classified in Level 1 in the fair value hierarchy. Notes payable consist of commercial paper borrowings and are not traded on an exchange; therefore, they are classified as Level 2 in the fair value hierarchy. The following table presents the carrying amounts and fair values of financial instruments not recorded at fair value on the Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 Carrying Amount Fair Value Carrying Amount Fair Value (in millions) Long-term debt, including current maturities (a) $ 4,248.8 $ 4,198.7 $ 4,401.2 $ 4,215.6 (a) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy. Carrying amount of long-term debt is net of deferred financing costs.

Other Comprehensive Income

Other Comprehensive Income	9 Months Ended
Other Comprehensive Income	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income	(9) Other Compr ehensive Income We record deferred gains (losses) in AOCI related to interest rate swaps designated as cash flow hedges, commodity contracts designated as cash flow hedges, and the amortization of components of our defined benefit plans. Deferred gains (losses) for our commodity contracts designated as cash flow hedges are recognized in earnings upon settlement, while deferred gains (losses) related to our interest rate swaps are recognized in earnings as they are amortized. The following table details reclassifications out of AOCI and into Net income. The amounts in parentheses below indicate decreases to Net income in the Consolidated Statements of Income for the period, net of tax: Amount Reclassified from AOCI Amount Reclassified from AOCI Location on the Consolidated Statements of Income Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 (in millions) Gains and (losses) on cash flow hedges: Interest rate swaps Interest expense $ ( 0.8 ) $ ( 0.7 ) $ ( 2.2 ) $ ( 2.1 ) Commodity contracts Fuel, purchased power, and cost of natural gas sold - - ( 3.2 ) ( 2.5 ) $ ( 0.8 ) $ ( 0.7 ) $ ( 5.4 ) $ ( 4.6 ) Income tax Income tax expense 0.2 0.1 1.2 1.1 Total reclassification adjustments related to cash flow hedges, net of tax $ ( 0.6 ) $ ( 0.6 ) $ ( 4.2 ) $ ( 3.5 ) Amortization of components of defined benefit plans: Actuarial (loss) Operations and maintenance - - ( 0.1 ) ( 0.1 ) $ - $ - $ ( 0.1 ) $ ( 0.1 ) Income tax Income tax expense - - - - Total reclassification adjustments related to defined benefit plans, net of tax $ - $ - $ ( 0.1 ) $ ( 0.1 ) Total reclassifications $ ( 0.6 ) $ ( 0.6 ) $ ( 4.3 ) $ ( 3.6 ) Balances by classification included within AOCI, net of tax on the accompanying Consolidated Balance Sheets were as follows: Derivatives Designated as Cash Flow Hedges Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total (in millions) As of December 31, 2023 $ ( 6.1 ) $ ( 2.5 ) $ ( 6.2 ) $ ( 14.8 ) Other comprehensive income (loss) before reclassifications - ( 0.1 ) - ( 0.1 ) Amounts reclassified from AOCI 1.7 2.5 0.1 4.3 As of September 30, 2024 $ ( 4.4 ) $ ( 0.1 ) $ ( 6.1 ) $ ( 10.6 ) Derivatives Designated as Cash Flow Hedges Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total (in millions) As of December 31, 2022 $ ( 8.3 ) $ ( 1.2 ) $ ( 6.1 ) $ ( 15.6 ) Other comprehensive income (loss) before reclassifications - ( 0.9 ) - ( 0.9 ) Amounts reclassified from AOCI 1.7 1.8 0.1 3.6 As of September 30, 2023 $ ( 6.6 ) $ ( 0.3 ) $ ( 6.0 ) $ ( 12.9 )

Employee Benefits Plans

Employee Benefits Plans	9 Months Ended
Employee Benefits Plans	Sep. 30, 2024
Retirement Benefits [Abstract]
Employee Benefit Plans	(10) Employe e Benefit Plans Components of Net Periodic Expense The components of net periodic expense were as follows: Defined Benefit Pension Plan Supplemental Non-qualified Defined Benefit Plans Non-pension Defined Benefit Postretirement Healthcare Plan Three Months Ended September 30, 2024 2023 2024 2023 2024 2023 (in millions) Service cost $ 0.6 $ 0.6 $ 1.3 $ ( 0.1 ) $ 0.4 $ 0.4 Interest cost 4.1 4.4 0.4 0.4 0.6 0.6 Expected return on plan assets ( 4.5 ) ( 4.7 ) - - ( 0.1 ) ( 0.1 ) Net amortization of prior service costs - - - - 0.1 - Recognized net actuarial loss 0.5 0.5 - - - - Net periodic expense $ 0.7 $ 0.8 $ 1.7 $ 0.3 $ 1.0 $ 0.9 Defined Benefit Pension Plan Supplemental Non-qualified Defined Benefit Plans Non-pension Defined Benefit Postretirement Healthcare Plan Nine Months Ended September 30, 2024 2023 2024 2023 2024 2023 (in millions) Service cost $ 1.7 $ 1.8 $ 2.9 $ 1.6 $ 1.2 $ 1.1 Interest cost 12.3 13.1 1.1 1.1 1.8 1.8 Expected return on plan assets ( 13.4 ) ( 14.0 ) - - ( 0.2 ) ( 0.1 ) Net amortization of prior service costs ( 0.1 ) - - - 0.1 - Recognized net actuarial loss 1.5 1.5 - - - - Net periodic expense $ 2.0 $ 2.4 $ 4.0 $ 2.7 $ 2.9 $ 2.8 Plan Contributions Contributions to the Defined Benefit Pension Plan are cash contributions made directly to the Pension Plan Trust account. Contributions to the Postretirement Healthcare and Supplemental Plans are primarily made in the form of benefit payments. Contributions made in the first nine months of 2024 and anticipated contributions for 2024 and 2025 are as follows: Contributions Made Additional Contributions Contributions Nine Months Ended September 30, 2024 Anticipated for Anticipated for (in millions) Defined Benefit Pension Plan $ 2.3 $ - $ 1.8 Non-pension Defined Benefit Postretirement Healthcare Plan $ 3.5 $ 1.2 $ 4.4 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans $ 1.8 $ 0.6 $ 2.8

Income Taxes

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	(11) Inco me Taxes Transfers of Production Tax Credits In August 2022, President Biden signed H.R. 5376 into law, commonly known as the Inflation Reduction Act of 2022, or IRA. The IRA contains a tax credit transferability provision that allows us to transfer (e.g. sell) PTCs produced after December 31, 2022, to third parties. In June 2024, under this transferability provision, we entered into an agreement with a third party to sell $ 16.9 million of our 2023 generated PTCs. We elected to account for the net proceeds from the transfer of PTCs as a reduction to income taxes payable under the scope of ASC 740 Income Taxes . We included the discount from the sale of our tax credits as a component of income tax expense. This sale of tax credits is presented within operating activities in the Consolidated Statement of Cash Flows consistent with the presentation of cash taxes paid. We expect to continue to explore the ability to efficiently monetize our tax credits through third party transferability agreements. We will also include any expected proceeds from the sale of tax credits in the evaluation of the realizability of deferred tax assets related to PTCs. IRS Revenue Procedure 2023-15 On April 14, 2023, the IRS released Revenue Procedure 2023-15 Amounts paid to improve tangible property . The Revenue Procedure provides a safe harbor method of accounting that taxpayers may use to determine whether costs to repair, maintain, replace, or improve natural gas transmission and distribution property must be capitalized. The Revenue Procedure may be adopted in tax years ending after May 1, 2023. We intend to elect the safe harbor for tax year 2024. We do not expect the Revenue Procedure to have a material impact on our tax repairs deduction. Income Tax Benefit (Expense) and Effective Tax Rates Three Months Ended September 30, 2024, Compared to the Three Months Ended September 30, 2023 Income tax (expense) for the three months ended September 30, 2024, was $( 2.9 ) million compared to $( 7.4 ) million reported for the same period in 2023. For the three months ended September 30, 2024, the effective tax rate was 10.0 % compared to 13.1 % for the same period in 2023. The lower effective tax rate was primarily driven by favorable return-to-accrual adjustments. Nine Months Ended September 30, 2024, Compared to the Nine Months Ended September 30, 2023 Income tax (expense) for the nine months ended September 30, 2024, was $( 23.6 ) million compared to $( 16.0 ) million reported for the same period in 2023. For the nine months ended September 30, 2024, the effective tax rate was 11.4 % which compared to 7.6 % for the same period in 2023 . The higher effective tax rate was primarily driven by a prior year $ 8.2 million tax benefit from a Nebraska income tax rate decrease.

Business Segment Information

Business Segment Information	9 Months Ended
Business Segment Information	Sep. 30, 2024
Segment Reporting Information, Additional Information [Abstract]
Business Segment Information	(12) Business Segme nt Information We conduct our business operations through two operating segments: Electric Utilities and Gas Utilities. Certain unallocated corporate expenses that support our operating segments are presented as Corporate and Other. Corporate and Other also includes business development activities that are not part of our operating segments and inter-segment eliminations. Our operating segments are equivalent to our reportable segments. Our Chief Executive Officer, who is considered to be our CODM, reviews financial information presented on an operating segment basis for purposes of making decisions, allocating resources, and assessing financial performance. Our CODM assesses the performance of our operating segments based on operating income. Our CODM reviews capital expenditures by operating segment rather than any individual or total asset amount. Segment information was as follows : Electric Utilities Gas Utilities Corporate and Other Total (in millions) Three Months Ended September 30, 2024 External revenues $ 229.6 $ 172.0 $ - $ 401.6 Inter-segment revenues 2.9 1.6 ( 4.5 ) - Operating income 65.1 10.9 ( 0.2 ) 75.8 Capital expenditures (a) 61.2 117.8 6.0 185.0 Three Months Ended September 30, 2023 External revenues $ 234.5 $ 172.6 $ - $ 407.1 Inter-segment revenues 2.8 1.7 ( 4.5 ) - Operating income 83.0 15.4 ( 0.6 ) 97.8 Capital expenditures (a) 55.7 108.1 1.3 165.1 Nine Months Ended September 30, 2024 External revenues $ 651.0 $ 879.6 $ - $ 1,530.6 Inter-segment revenues 8.8 4.6 ( 13.4 ) - Operating income 176.0 164.6 ( 0.8 ) 339.8 Capital expenditures (a) 246.8 308.2 10.8 565.8 Nine Months Ended September 30, 2023 External revenues $ 640.6 $ 1,099.0 $ - $ 1,739.6 Inter-segment revenues 8.5 4.9 ( 13.4 ) - Operating income 190.7 147.7 ( 2.2 ) 336.2 Capital expenditures (a) 155.6 260.9 4.1 420.6 (a) Includes accruals for property, plant, and equipment as disclosed in supplemental cash flow information in the Consolidated Statements of Cash Flows in the Consolidated Financial Statements.

Selected Balance Sheet Informat

Selected Balance Sheet Information	9 Months Ended
Selected Balance Sheet Information	Sep. 30, 2024
Selected Balance Sheet Information [Abstract]
Selected Balance Sheet Information	(13) Selected Balan ce Sheet Information Accounts Receivable and Allowance for Credit Losses Following is a summary of Accounts receivable, net included in the accompanying Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 (in millions) Billed Accounts Receivable $ 136.9 $ 198.5 Unbilled Revenue 69.9 154.0 Less: Allowance for Credit Losses ( 1.4 ) ( 2.2 ) Account Receivable, net $ 205.4 $ 350.3 Changes to allowance for credit losses for the nine months ended September 30, 2024 and 2023, respectively, were as follows: Balance at Beginning of Year Additions Charged to Costs and Expenses Recoveries and Other Additions Write-offs and Other Deductions Balance at September 30, (in millions) 2024 $ 2.2 $ 4.0 $ 2.8 $ ( 7.6 ) $ 1.4 2023 $ 3.0 $ 7.2 $ 2.4 $ ( 10.8 ) $ 1.8 Materials, Supplies, and Fuel The following amounts by major classification are included in Materials, supplies, and fuel on the accompanying Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 (in millions) Materials and supplies $ 103.9 $ 105.9 Fuel - Electric Utilities 7.6 7.7 Natural gas in storage 43.9 47.3 Total materials, supplies, and fuel $ 155.4 $ 160.9 Accrued Liabilities The following amounts by major classification are included in Accrued liabilities on the accompanying Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 (in millions) Accrued employee compensation, benefits, and withholdings $ 78.8 $ 74.8 Accrued property taxes 47.7 52.7 Customer deposits and prepayments 59.2 76.0 Accrued interest 60.4 46.3 Other (none of which is individually significant) 45.6 43.5 Total accrued liabilities $ 291.7 $ 293.3

Subsequent Events

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2024
Subsequent Events [Abstract]
Subsequent Events	(14) Subsequent Events Except as described in Notes 1 and 2 , there have been no events subsequent to September 30, 2024, which would require recognition in the Consolidated Financial Statements or disclosures.

Management's Statement (Policie

Management's Statement (Policies)	9 Months Ended
Management's Statement (Policies)	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of Estimates and Basis of Presentation	Use of Estimates and Basis of Presentation The information furnished in the accompanying Consolidated Financial Statements reflects certain estimates required and all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the September 30, 2024, December 31, 2023, and September 30, 2023 , financial information. Certain lines of business in which we operate are highly seasonal and our interim results of operations are not necessarily indicative of the results of operations to be expected for an entire year.
Recently Issued Accounting Standards	Recently Issued Accounting Standards Improvements to Reportable Segment Disclosures, ASU 2023-07 In November 2023, the FASB issued ASU 2023-07, Improvements to Reportable Segment Disclosures , which expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly reviewed by the CODM and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. ASU 2023-07 also allows, in addition to the measure that is most consistent with GAAP, the disclosure of additional measures of segment profit or loss that are used by the CODM in assessing segment performance and deciding how to allocate resources. ASU 2023-07 is effective for our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, and subsequent interim periods, with early adoption permitted. We do not expect ASU 2023-07 to have an impact on our financial position, results of operations and cash flows; however, are currently evaluating the impact on our consolidated financial statement disclosures. Improvements to Income Tax Disclosures, ASU 2023-09 In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures , which expands public entities’ annual disclosures by requiring disclosure of tax rate reconciliation amounts and percentages for specific categories, income taxes paid disaggregated by federal and state taxes, and income tax expense disaggregated by federal and state taxes jurisdiction. ASU 2023-09 is effective for our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, with early adoption permitted. We do not expect ASU 2023-09 to have an impact on our financial position, results of operations and cash flows; however, are currently evaluating the impact on our consolidated financial statement disclosures.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
Regulatory Matters (Tables)	Sep. 30, 2024
Regulated Operations [Abstract]
Schedule of Regulatory Assets and Liabilities	We had the following regulatory assets and liabilities: As of As of September 30, 2024 December 31, 2023 (in millions) Regulatory assets Winter Storm Uri $ 123.4 $ 199.6 Deferred energy and fuel cost adjustments 61.1 55.1 Deferred gas cost adjustments 17.2 4.1 Gas price derivatives 3.2 5.1 Deferred taxes on AFUDC 7.7 7.1 Employee benefit plans and related deferred taxes 86.1 89.3 Environmental 10.6 2.9 Loss on reacquired debt 16.1 17.4 Deferred taxes on flow through accounting 80.9 74.7 Decommissioning costs 2.4 2.4 Other regulatory assets 23.5 22.4 Total regulatory assets 432.2 480.1 Less current regulatory assets ( 156.1 ) ( 175.7 ) Regulatory assets, non-current $ 276.1 $ 304.4 Regulatory liabilities Deferred energy and gas costs $ 82.6 $ 88.9 Employee benefit plan costs and related deferred taxes 34.6 36.2 Cost of removal 193.2 181.9 Excess deferred income taxes 240.5 247.1 Other regulatory liabilities 6.1 12.5 Total regulatory liabilities 557.0 566.6 Less current regulatory liabilities ( 86.2 ) ( 98.9 ) Regulatory liabilities, non-current $ 470.8 $ 467.7

Revenue (Tables)

Revenue (Tables)	9 Months Ended
Revenue (Tables)	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables depict the disaggregation of revenue, including intercompany revenue, from contracts with customers by customer type and timing of revenue recognition for each of the reportable segments for the three and nine months ended September 30, 2024, and 2023. Sales tax and other similar taxes are excluded from revenues. Three Months Ended September 30, 2024 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 195.5 $ 117.4 $ - $ 312.9 Transportation - 43.2 ( 0.2 ) 43.0 Wholesale 6.2 - - 6.2 Market - off-system sales 10.8 - - 10.8 Transmission/Other 19.1 10.9 ( 4.3 ) 25.7 Revenue from contracts with customers $ 231.6 $ 171.5 $ ( 4.5 ) $ 398.6 Other revenues 0.9 2.1 - 3.0 Total revenues $ 232.5 $ 173.6 $ ( 4.5 ) $ 401.6 Timing of revenue recognition: Services transferred at a point in time $ 9.3 $ - $ - $ 9.3 Services transferred over time 222.3 171.5 ( 4.5 ) 389.3 Revenue from contracts with customers $ 231.6 $ 171.5 $ ( 4.5 ) $ 398.6 Three Months Ended September 30, 2023 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 191.0 $ 120.8 $ - $ 311.8 Transportation - 42.7 ( 0.1 ) 42.6 Wholesale 9.4 - - 9.4 Market - off-system sales 13.0 - - 13.0 Transmission/Other 18.1 9.6 ( 4.4 ) 23.3 Revenue from contracts with customers $ 231.5 $ 173.1 $ ( 4.5 ) $ 400.1 Other revenues 5.8 1.2 - 7.0 Total revenues $ 237.3 $ 174.3 $ ( 4.5 ) $ 407.1 Timing of revenue recognition: Services transferred at a point in time $ 7.8 $ - $ - $ 7.8 Services transferred over time 223.7 173.1 ( 4.5 ) 392.3 Revenue from contracts with customers $ 231.5 $ 173.1 $ ( 4.5 ) $ 400.1 Nine Months Ended September 30, 2024 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 555.1 $ 707.7 $ - $ 1,262.8 Transportation - 130.8 ( 0.3 ) 130.5 Wholesale 21.2 - - 21.2 Market - off-system sales 22.8 0.1 - 22.9 Transmission/Other 56.6 32.1 ( 13.1 ) 75.6 Revenue from contracts with customers $ 655.7 $ 870.7 $ ( 13.4 ) $ 1,513.0 Other revenues 4.1 13.5 - 17.6 Total revenues $ 659.8 $ 884.2 $ ( 13.4 ) $ 1,530.6 Timing of revenue recognition: Services transferred at a point in time $ 25.9 $ - $ - $ 25.9 Services transferred over time 629.8 870.7 ( 13.4 ) 1,487.1 Revenue from contracts with customers $ 655.7 $ 870.7 $ ( 13.4 ) $ 1,513.0 Nine Months Ended September 30, 2023 Electric Utilities Gas Utilities Inter-segment Eliminations Total Customer types: (in millions) Retail $ 522.3 $ 931.1 $ - $ 1,453.4 Transportation - 131.4 ( 0.3 ) 131.1 Wholesale 24.6 - - 24.6 Market - off-system sales 37.5 0.4 - 37.9 Transmission/Other 54.7 28.8 ( 13.1 ) 70.4 Revenue from contracts with customers $ 639.1 $ 1,091.7 $ ( 13.4 ) $ 1,717.4 Other revenues 10.0 12.2 - 22.2 Total revenues $ 649.1 $ 1,103.9 $ ( 13.4 ) $ 1,739.6 Timing of revenue recognition: Services transferred at a point in time $ 24.3 $ - $ - $ 24.3 Services transferred over time 614.8 1,091.7 ( 13.4 ) 1,693.1 Revenue from contracts with customers $ 639.1 $ 1,091.7 $ ( 13.4 ) $ 1,717.4

Financing (Tables)

Financing (Tables)	9 Months Ended
Financing (Tables)	Sep. 30, 2024
Debt Disclosure [Abstract]
Schedule of Short-term Debt	Our Revolving Credit Facility and CP Program, which are classified as Notes payable on the Consolidated Balance Sheets, had the following borrowings, outstanding letters of credit, and available capacity as of: September 30, 2024 December 31, 2023 (dollars in millions) Amount outstanding $ 17.5 $ - Letters of credit (a) $ 3.5 $ 3.7 Available capacity $ 729.0 $ 746.3 Weighted average interest rates 4.93 % N/A (a) Letters of credit are off-balance sheet commitments that reduce the borrowing capacity available on our corporate Revolving Credit Facility . Revolving Credit Facility and CP Program borrowing activity was as follows: Nine Months Ended September 30, 2024 2023 (dollars in millions) Maximum amount outstanding (based on daily outstanding balances) $ 25.8 $ 548.7 Average amount outstanding (based on daily outstanding balances) $ 0.6 $ 109.2 Weighted average interest rates 5.15 % 4.91 %
Summary of ATM Activity	ATM activity was as follows: Three Months Ended September 30, Nine Months Ended September 30, 2024 (a) 2023 2024 (a) 2023 August 4, 2020 ATM Program (in millions, except Average price per share amounts) Proceeds, (net of issuance costs of $ 0.0 , $ 0.0 , $ 0.0 , and $( 0.5 ), respectively) $ - $ - $ - $ 48.5 Number of shares issued - - - 0.8 June 16, 2023 ATM Program Proceeds, (net of issuance costs of $( 1.1 ), $( 0.5 ), $( 1.8 ), and $( 0.6 ), respectively) $ 108.6 $ 52.8 $ 181.6 $ 59.2 Number of shares issued 1.9 0.9 3.3 1.0 Total activity under both ATM Programs Proceeds, (net of issuance costs of $( 1.1 ), $( 0.5 ), $( 1.8 ), and $( 1.1 ), respectively) $ 108.6 $ 52.8 $ 181.6 $ 107.7 Number of shares issued 1.9 0.9 3.3 1.8 Average price per share $ 56.84 $ 57.33 $ 55.63 $ 60.02 (a) In August 2024, we executed a block trade, which completed our planned equity issuances for 2024.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
Earnings Per Share (Tables)	Sep. 30, 2024
Earnings Per Share [Abstract]
Schedule of Earnings Per Share Reconciliation	A reconciliation of share amounts used to compute earnings per share in the accompanying Consolidated Statements of Income was as follows: Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 (in millions, except per share amounts) Net income available for common stock $ 24.4 $ 45.4 $ 175.0 $ 182.5 Weighted average shares - basic 70.5 67.3 69.2 66.7 Dilutive effect of equity compensation 0.1 0.1 0.1 - Weighted average shares - diluted 70.6 67.4 69.3 66.7 Net income available for common stock, per share - Diluted $ 0.35 $ 0.67 $ 2.52 $ 2.74
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following securities were excluded from the diluted earnings per share computation because of their anti-dilutive nature: Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 (in millions of shares) Equity compensation - 0.1 - - Restricted stock - - - - Anti-dilutive shares excluded from computation of earnings per share - 0.1 - -

Risk Management And Derivativ_2

Risk Management And Derivatives (Tables)	9 Months Ended
Risk Management And Derivatives (Tables)	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Contract or notional amounts and terms of marketing activities and derivative commodity instruments	The contract or notional amounts and terms of the electric and natural gas derivative commodity instruments held at our Utilities are composed of both long and short positions. We had the following net long and (short) positions as of: September 30, 2024 December 31, 2023 Notional Amounts (MMBtus) Maximum Term (months) (a) Notional Amounts (MMBtus) Maximum Term (months) (a) Natural gas futures purchased 1,800,000 6 650,000 3 Natural gas options purchased, net 7,680,000 6 2,850,000 3 Natural gas basis swaps purchased 1,800,000 6 1,050,000 3 Natural gas over-the-counter swaps, net (b) 4,890,000 22 3,890,000 21 Natural gas physical contracts, net (c) 32,240,665 6 12,582,415 10 (a) Term reflects the maximum forward period hedged. (b) As of September 30, 2024 , 2,276,000 MMBtus of natural gas over-the-counter swaps purchases were designated as cash flow hedges. (c) Volumes exclude derivative contracts that qualify for the normal purchases and normal sales exception permitted by GAAP.
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table presents the fair value and balance sheet classification of our derivative instruments as of: Balance Sheet Location September 30, December 31, (in millions) Derivatives designated as hedges: Liability derivative instruments: Current commodity derivatives Derivative liabilities, current $ ( 0.6 ) $ ( 2.7 ) Noncurrent commodity derivatives Other assets, non-current - ( 0.2 ) Total derivatives designated as hedges $ ( 0.6 ) $ ( 2.9 ) Derivatives not designated as hedges: Liability derivative instruments: Current commodity derivatives Derivative liabilities, current $ ( 3.9 ) $ ( 3.8 ) Noncurrent commodity derivatives Other deferred credits and other liabilities ( 0.1 ) ( 0.1 ) Total derivatives not designated as hedges $ ( 4.0 ) $ ( 3.9 )
Derivative Instruments, Gain (Loss)	The impact of cash flow hedges on our Consolidated Statements of Comprehensive Income and Consolidated Statements of Income are presented below for the three and nine months ended September 30, 2024, and 2023. Note that this presentation does not reflect the gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended Three Months Ended 2024 2023 2024 2023 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in OCI Income Statement Location Amount of Gain/(Loss) Reclassified from AOCI into Income (in millions) (in millions) Interest rate swaps $ 0.8 $ 0.7 Interest expense $ ( 0.8 ) $ ( 0.7 ) Commodity derivatives 0.1 ( 0.2 ) Fuel, purchased power, and cost of natural gas sold - - Total $ 0.9 $ 0.5 $ ( 0.8 ) $ ( 0.7 ) Nine Months Ended Nine Months Ended 2024 2023 2024 2023 Derivatives in Cash Flow Hedging Relationships Amount of Gain/(Loss) Recognized in OCI Income Statement Location Amount of Gain/(Loss) Reclassified from AOCI into Income (in millions) (in millions) Interest rate swaps $ 2.2 $ 2.1 I nterest expense $ ( 2.2 ) $ ( 2.1 ) Commodity derivatives 3.1 1.3 Fuel, purchased power, and cost of natural gas sold ( 3.2 ) ( 2.5 ) Total $ 5.3 $ 3.4 $ ( 5.4 ) $ ( 4.6 ) As of September 30, 2024, $ 2.9 million o f net losses related to our interest rate swaps and commodity derivatives are expected to be reclassified from AOCI into earnings within the next 12 months. As market prices fluctuate, estimated and actual realized gains or losses will change during future periods. Derivatives Not Designated as Hedge Instruments The following table summarizes the impacts of derivative instruments not designated as hedge instruments on our Consolidated Statements of Income for the three and nine months ended September 30, 2024, and 2023. Note that this presentation does not reflect the expected gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended September 30, 2024 2023 Derivatives Not Designated as Hedging Instruments Location of Gain/(Loss) on Derivatives Recognized in Income Amount of Gain/(Loss) on Derivatives Recognized in Income (in millions) Commodity derivatives Fuel, purchased power, and cost of natural gas sold $ ( 0.3 ) $ 0.3 $ ( 0.3 ) $ 0.3 Nine Months Ended September 30, 2024 2023 Derivatives Not Designated as Hedging Instruments Location of Gain/(Loss) on Derivatives Recognized in Income Amount of Gain/(Loss) on Derivatives Recognized in Income (in millions) Commodity derivatives Fuel, purchased power, and cost of natural gas sold $ 0.4 $ ( 2.4 ) $ 0.4 $ ( 2.4 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value Hierarchy, Measured on Recurring Basis	The following tables set forth, by level within the fair value hierarchy, our gross assets and gross liabilities and related offsetting as permitted by GAAP that were accounted for at fair value on a recurring basis for derivative instruments. As of September 30, 2024 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting (a) Total (in millions) Assets: Commodity derivatives - Gas Utilities $ - $ 5.6 $ - $ ( 5.6 ) $ - Total $ - $ 5.6 $ - $ ( 5.6 ) $ - Liabilities: Commodity derivatives - Gas Utilities $ - $ 5.7 $ - $ ( 1.1 ) $ 4.6 Total $ - $ 5.7 $ - $ ( 1.1 ) $ 4.6 (a) As of September 30, 2024, $ 5.6 million of our commodity derivative assets and $ 1.1 million of our commodity derivative liabilities, as well as related gross collateral amounts, were subject to master netting agreements. As of December 31, 2023 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting (a) Total (in millions) Assets: Commodity derivatives - Gas Utilities $ - $ 1.9 $ - $ ( 1.9 ) $ - Total $ - $ 1.9 $ - $ ( 1.9 ) $ - Liabilities: Commodity derivatives - Gas Utilities $ - $ 10.1 $ - $ ( 3.3 ) $ 6.8 Total $ - $ 10.1 $ - $ ( 3.3 ) $ 6.8 (a) As of December 31, 2023 , $ 1.9 million of our commodity derivative assets and $ 3.3 million of our commodity derivative liabilities, as well as related gross collateral amounts, were subject to master netting agreements.
Fair Value, by Balance Sheet Grouping	The following table presents the carrying amounts and fair values of financial instruments not recorded at fair value on the Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 Carrying Amount Fair Value Carrying Amount Fair Value (in millions) Long-term debt, including current maturities (a) $ 4,248.8 $ 4,198.7 $ 4,401.2 $ 4,215.6 (a) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified in Level 2 in the fair value hierarchy. Carrying amount of long-term debt is net of deferred financing costs.

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	9 Months Ended
Other Comprehensive Income (Tables)	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
Reclassification out of Accumulated Other Comprehensive Income	The following table details reclassifications out of AOCI and into Net income. The amounts in parentheses below indicate decreases to Net income in the Consolidated Statements of Income for the period, net of tax: Amount Reclassified from AOCI Amount Reclassified from AOCI Location on the Consolidated Statements of Income Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 (in millions) Gains and (losses) on cash flow hedges: Interest rate swaps Interest expense $ ( 0.8 ) $ ( 0.7 ) $ ( 2.2 ) $ ( 2.1 ) Commodity contracts Fuel, purchased power, and cost of natural gas sold - - ( 3.2 ) ( 2.5 ) $ ( 0.8 ) $ ( 0.7 ) $ ( 5.4 ) $ ( 4.6 ) Income tax Income tax expense 0.2 0.1 1.2 1.1 Total reclassification adjustments related to cash flow hedges, net of tax $ ( 0.6 ) $ ( 0.6 ) $ ( 4.2 ) $ ( 3.5 ) Amortization of components of defined benefit plans: Actuarial (loss) Operations and maintenance - - ( 0.1 ) ( 0.1 ) $ - $ - $ ( 0.1 ) $ ( 0.1 ) Income tax Income tax expense - - - - Total reclassification adjustments related to defined benefit plans, net of tax $ - $ - $ ( 0.1 ) $ ( 0.1 ) Total reclassifications $ ( 0.6 ) $ ( 0.6 ) $ ( 4.3 ) $ ( 3.6 )
Schedule of Accumulated Other Comprehensive Income (Loss)	Balances by classification included within AOCI, net of tax on the accompanying Consolidated Balance Sheets were as follows: Derivatives Designated as Cash Flow Hedges Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total (in millions) As of December 31, 2023 $ ( 6.1 ) $ ( 2.5 ) $ ( 6.2 ) $ ( 14.8 ) Other comprehensive income (loss) before reclassifications - ( 0.1 ) - ( 0.1 ) Amounts reclassified from AOCI 1.7 2.5 0.1 4.3 As of September 30, 2024 $ ( 4.4 ) $ ( 0.1 ) $ ( 6.1 ) $ ( 10.6 ) Derivatives Designated as Cash Flow Hedges Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total (in millions) As of December 31, 2022 $ ( 8.3 ) $ ( 1.2 ) $ ( 6.1 ) $ ( 15.6 ) Other comprehensive income (loss) before reclassifications - ( 0.9 ) - ( 0.9 ) Amounts reclassified from AOCI 1.7 1.8 0.1 3.6 As of September 30, 2023 $ ( 6.6 ) $ ( 0.3 ) $ ( 6.0 ) $ ( 12.9 )

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
Employee Benefit Plans (Tables)	Sep. 30, 2024
Defined Benefit Plan Disclosure [Line Items]
Components of Net Periodic Benefit Cost	The components of net periodic expense were as follows: Defined Benefit Pension Plan Supplemental Non-qualified Defined Benefit Plans Non-pension Defined Benefit Postretirement Healthcare Plan Three Months Ended September 30, 2024 2023 2024 2023 2024 2023 (in millions) Service cost $ 0.6 $ 0.6 $ 1.3 $ ( 0.1 ) $ 0.4 $ 0.4 Interest cost 4.1 4.4 0.4 0.4 0.6 0.6 Expected return on plan assets ( 4.5 ) ( 4.7 ) - - ( 0.1 ) ( 0.1 ) Net amortization of prior service costs - - - - 0.1 - Recognized net actuarial loss 0.5 0.5 - - - - Net periodic expense $ 0.7 $ 0.8 $ 1.7 $ 0.3 $ 1.0 $ 0.9 Defined Benefit Pension Plan Supplemental Non-qualified Defined Benefit Plans Non-pension Defined Benefit Postretirement Healthcare Plan Nine Months Ended September 30, 2024 2023 2024 2023 2024 2023 (in millions) Service cost $ 1.7 $ 1.8 $ 2.9 $ 1.6 $ 1.2 $ 1.1 Interest cost 12.3 13.1 1.1 1.1 1.8 1.8 Expected return on plan assets ( 13.4 ) ( 14.0 ) - - ( 0.2 ) ( 0.1 ) Net amortization of prior service costs ( 0.1 ) - - - 0.1 - Recognized net actuarial loss 1.5 1.5 - - - - Net periodic expense $ 2.0 $ 2.4 $ 4.0 $ 2.7 $ 2.9 $ 2.8
Schedule of Employer Contribution to Employee Benefit Plans	Contributions made in the first nine months of 2024 and anticipated contributions for 2024 and 2025 are as follows: Contributions Made Additional Contributions Contributions Nine Months Ended September 30, 2024 Anticipated for Anticipated for (in millions) Defined Benefit Pension Plan $ 2.3 $ - $ 1.8 Non-pension Defined Benefit Postretirement Healthcare Plan $ 3.5 $ 1.2 $ 4.4 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans $ 1.8 $ 0.6 $ 2.8

Business Segment Information (T

Business Segment Information (Tables)	9 Months Ended
Business Segment Information (Tables)	Sep. 30, 2024
Segment Reporting Information, Additional Information [Abstract]
Segment information included in Consolidated Statements of Income	Segment information was as follows : Electric Utilities Gas Utilities Corporate and Other Total (in millions) Three Months Ended September 30, 2024 External revenues $ 229.6 $ 172.0 $ - $ 401.6 Inter-segment revenues 2.9 1.6 ( 4.5 ) - Operating income 65.1 10.9 ( 0.2 ) 75.8 Capital expenditures (a) 61.2 117.8 6.0 185.0 Three Months Ended September 30, 2023 External revenues $ 234.5 $ 172.6 $ - $ 407.1 Inter-segment revenues 2.8 1.7 ( 4.5 ) - Operating income 83.0 15.4 ( 0.6 ) 97.8 Capital expenditures (a) 55.7 108.1 1.3 165.1 Nine Months Ended September 30, 2024 External revenues $ 651.0 $ 879.6 $ - $ 1,530.6 Inter-segment revenues 8.8 4.6 ( 13.4 ) - Operating income 176.0 164.6 ( 0.8 ) 339.8 Capital expenditures (a) 246.8 308.2 10.8 565.8 Nine Months Ended September 30, 2023 External revenues $ 640.6 $ 1,099.0 $ - $ 1,739.6 Inter-segment revenues 8.5 4.9 ( 13.4 ) - Operating income 190.7 147.7 ( 2.2 ) 336.2 Capital expenditures (a) 155.6 260.9 4.1 420.6 (a) Includes accruals for property, plant, and equipment as disclosed in supplemental cash flow information in the Consolidated Statements of Cash Flows in the Consolidated Financial Statements.

Selected Balance Sheet Inform_2

Selected Balance Sheet Information (Tables)	9 Months Ended
Selected Balance Sheet Information (Tables)	Sep. 30, 2024
Selected Balance Sheet Information [Abstract]
Account Receivable Schedule	Following is a summary of Accounts receivable, net included in the accompanying Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 (in millions) Billed Accounts Receivable $ 136.9 $ 198.5 Unbilled Revenue 69.9 154.0 Less: Allowance for Credit Losses ( 1.4 ) ( 2.2 ) Account Receivable, net $ 205.4 $ 350.3
Financing Receivable, Current, Allowance for Credit Loss	Changes to allowance for credit losses for the nine months ended September 30, 2024 and 2023, respectively, were as follows: Balance at Beginning of Year Additions Charged to Costs and Expenses Recoveries and Other Additions Write-offs and Other Deductions Balance at September 30, (in millions) 2024 $ 2.2 $ 4.0 $ 2.8 $ ( 7.6 ) $ 1.4 2023 $ 3.0 $ 7.2 $ 2.4 $ ( 10.8 ) $ 1.8
Materials, Supplies and Fuel	The following amounts by major classification are included in Materials, supplies, and fuel on the accompanying Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 (in millions) Materials and supplies $ 103.9 $ 105.9 Fuel - Electric Utilities 7.6 7.7 Natural gas in storage 43.9 47.3 Total materials, supplies, and fuel $ 155.4 $ 160.9
Schedule of Accrued Liabilities	The following amounts by major classification are included in Accrued liabilities on the accompanying Consolidated Balance Sheets as of: September 30, 2024 December 31, 2023 (in millions) Accrued employee compensation, benefits, and withholdings $ 78.8 $ 74.8 Accrued property taxes 47.7 52.7 Customer deposits and prepayments 59.2 76.0 Accrued interest 60.4 46.3 Other (none of which is individually significant) 45.6 43.5 Total accrued liabilities $ 291.7 $ 293.3

Regulatory Matters_ Regulatory

Regulatory Matters: Regulatory Matters (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Regulatory assets	$ 432.2	$ 480.1
Regulatory assets, current	(156.1)	(175.7)
Regulatory assets, non-current	276.1	304.4
Regulatory liabilities	557	566.6
Regulatory liabilities, current	(86.2)	(98.9)
Regulatory liabilities, non-current	470.8	467.7
Deferred energy and gas costs
Regulatory liabilities	82.6	88.9
Employee benefit plan costs and related deferred taxes
Regulatory liabilities	34.6	36.2
Cost of removal
Regulatory liabilities	193.2	181.9
Excess deferred income taxes
Regulatory liabilities	240.5	247.1
Other regulatory liabilities
Regulatory liabilities	6.1	12.5
Storm Costs
Regulatory assets	123.4	199.6
Deferred energy and gas costs
Regulatory assets	61.1	55.1
Deferred gas cost adjustments
Regulatory assets	17.2	4.1
Gas price derivatives
Regulatory assets	3.2	5.1
Deferred taxes on AFUDC
Regulatory assets	7.7	7.1
Employee benefit plans and related deferred taxes
Regulatory assets	86.1	89.3
Environmental
Regulatory assets	10.6	2.9
Loss on reacquired debt
Regulatory assets	16.1	17.4
Deferred taxes on flow through accounting
Regulatory assets	80.9	74.7
Decommissioning costs
Regulatory assets	2.4	2.4
Other regulatory assets
Regulatory assets	$ 23.5	$ 22.4

Regulatory Matters_ Gas Utiliti

Regulatory Matters: Gas Utilities Regulatory Activity (Details) $ in Millions					1 Months Ended
	Oct. 15, 2024 USD ($)	Oct. 01, 2024 USD ($)	Jun. 14, 2024 USD ($) mi	Jan. 17, 2024 USD ($)	Mar. 31, 2024 USD ($)	May 01, 2024 mi	Dec. 04, 2023 mi	May 18, 2023 mi	May 09, 2023 mi
Colorado Public Utilities Commission (CPUC) \| Black Hills Energy - Colorado Gas \| Rate Review Filed with the Regulatory Agency
Public Utilities, General Disclosures [Line Items]
Public Utilities - Length of Natural Gas Pipeline to Receive Infrastructure Investments \| mi									10,000
Colorado Public Utilities Commission (CPUC) \| Black Hills Energy - Colorado Gas \| Settlement Reached with the Regulatory Agency
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Equity Capital Structure, Percentage					51%
Public Utilities, Approved Debt Capital Structure, Percentage					49%
Public Utilities, Approved Return on Equity, Percentage					9.30%
Public Utilities, Approved Rate Increase (Decrease), Amount \| $					$ 20.2
Colorado Public Utilities Commission (CPUC) \| Black Hills Energy - Colorado Electric \| Rate Review Filed with the Regulatory Agency
Public Utilities, General Disclosures [Line Items]
Public Utilities - Length of Electric Distribution Lines to Receive Infrastructure Investments \| mi			3,200
Public Utilities - Length of Electric Transmission Lines to Receive Infrastructure Investments \| mi			600
Public Utilities, Requested Rate Increase (Decrease), Amount \| $			$ 36.7
Public utilities, requested equity capital structure, percentage			53%
Public utilities, requested debt capital structure, percentage			47%
Public Utilities, Requested Return on Equity, Percentage			10.50%
Iowa Utilities Commission (IUC) \| Black Hills Energy - Iowa Gas \| Rate Review Filed with the Regulatory Agency
Public Utilities, General Disclosures [Line Items]
Public Utilities - Length of Natural Gas Pipeline to Receive Infrastructure Investments \| mi						5,000
Arkansas Public Service Commission \| Black Hills Energy - Arkansas Gas \| Rate Review Filed with the Regulatory Agency
Public Utilities, General Disclosures [Line Items]
Public Utilities - Length of Natural Gas Pipeline to Receive Infrastructure Investments \| mi							7,200
Wyoming Public Service Commission \| Black Hills Energy - Wyoming Gas \| WPSC Approved a Settlement Agreement for a General Rate Increase
Public Utilities, General Disclosures [Line Items]
Public Utilities - Length of Natural Gas Pipeline to Receive Infrastructure Investments \| mi								6,400
Public Utilities, Approved Equity Capital Structure, Percentage				51%
Public Utilities, Approved Debt Capital Structure, Percentage				49%
Public Utilities, Approved Return on Equity, Percentage				9.90%
Public Utilities, Approved Rate Increase (Decrease), Amount \| $				$ 13.9
Extension period as per settlement agreement				4 years
Subsequent Event \| Iowa Utilities Commission (IUC) \| Black Hills Energy - Iowa Gas \| Reached a Global Settlement Agreement with the Iowa Office of Consumer Advocate for a General Rate Increase, which is Subject to IUC Approval
Public Utilities, General Disclosures [Line Items]
Public Utilities Weighted average cost of capital percentage	7.20%
Public Utilities, Approved Rate Increase (Decrease), Amount \| $	$ 15
Subsequent Event \| Arkansas Public Service Commission \| Black Hills Energy - Arkansas Gas \| Received Final Approval for a Settlement Agreement for a General Rate Increase
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Equity Capital Structure, Percentage		46%
Public Utilities, Approved Debt Capital Structure, Percentage		54%
Public Utilities, Requested Return on Equity, Percentage		9.90%
Public Utilities, Approved Rate Increase (Decrease), Amount \| $		$ 25.4
Public Utilities, Approved Shift Rate Rider Rate to Base Rate \| $		$ 3.7

Commitment, Contingencies And_2

Commitment, Contingencies And Guarantees (Additional Information) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
Accrued liabilities	$ 291.7	$ 293.3
Regulatory assets	432.2	480.1
Environmental
Loss Contingencies [Line Items]
Regulatory assets	10.6	$ 2.9
Manufactured Gas Plant
Loss Contingencies [Line Items]
Insurance Settlements Receivable, Noncurrent	1.5
Site remediation cost	7.4
Accrued liabilities	11.5
Regulatory assets	$ 10.6

Revenue_ Disaggregation of Reve

Revenue: Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue from contracts with customers	$ 398.6	$ 400.1	$ 1,513	$ 1,717.4
Revenue	401.6	407.1	1,530.6	1,739.6
Retail - Electric , Natural Gas and Coal
Revenue from contracts with customers	312.9	311.8	1,262.8	1,453.4
Transportation
Revenue from contracts with customers	43	42.6	130.5	131.1
Wholesale
Revenue from contracts with customers	6.2	9.4	21.2	24.6
Market - off-system sales
Revenue from contracts with customers	10.8	13	22.9	37.9
Transmission/Other
Revenue from contracts with customers	25.7	23.3	75.6	70.4
Other revenues
Revenue	3	7	17.6	22.2
Services transferred at a point in time
Revenue from contracts with customers	9.3	7.8	25.9	24.3
Services transferred over time
Revenue from contracts with customers	389.3	392.3	1,487.1	1,693.1
Inter-segment Eliminations
Revenue from contracts with customers	(4.5)	(4.5)	(13.4)	(13.4)
Revenue	(4.5)	(4.5)	(13.4)	(13.4)
Inter-segment Eliminations \| Retail - Electric , Natural Gas and Coal
Revenue from contracts with customers	0	0	0	0
Inter-segment Eliminations \| Transportation
Revenue from contracts with customers	(0.2)	(0.1)	(0.3)	(0.3)
Inter-segment Eliminations \| Wholesale
Revenue from contracts with customers	0	0	0	0
Inter-segment Eliminations \| Market - off-system sales
Revenue from contracts with customers	0	0	0	0
Inter-segment Eliminations \| Transmission/Other
Revenue from contracts with customers	(4.3)	(4.4)	(13.1)	(13.1)
Inter-segment Eliminations \| Other revenues
Revenue	0	0	0	0
Inter-segment Eliminations \| Services transferred at a point in time
Revenue from contracts with customers	0	0	0	0
Inter-segment Eliminations \| Services transferred over time
Revenue from contracts with customers	(4.5)	(4.5)	(13.4)	(13.4)
Operating Segments \| Electric Utilities
Revenue from contracts with customers	231.6	231.5	655.7	639.1
Revenue	232.5	237.3	659.8	649.1
Operating Segments \| Electric Utilities \| Retail - Electric , Natural Gas and Coal
Revenue from contracts with customers	195.5	191	555.1	522.3
Operating Segments \| Electric Utilities \| Transportation
Revenue from contracts with customers	0	0	0	0
Operating Segments \| Electric Utilities \| Wholesale
Revenue from contracts with customers	6.2	9.4	21.2	24.6
Operating Segments \| Electric Utilities \| Market - off-system sales
Revenue from contracts with customers	10.8	13	22.8	37.5
Operating Segments \| Electric Utilities \| Transmission/Other
Revenue from contracts with customers	19.1	18.1	56.6	54.7
Operating Segments \| Electric Utilities \| Other revenues
Revenue	0.9	5.8	4.1	10
Operating Segments \| Electric Utilities \| Services transferred at a point in time
Revenue from contracts with customers	9.3	7.8	25.9	24.3
Operating Segments \| Electric Utilities \| Services transferred over time
Revenue from contracts with customers	222.3	223.7	629.8	614.8
Operating Segments \| Gas Utilities
Revenue from contracts with customers	171.5	173.1	870.7	1,091.7
Revenue	173.6	174.3	884.2	1,103.9
Operating Segments \| Gas Utilities \| Retail - Electric , Natural Gas and Coal
Revenue from contracts with customers	117.4	120.8	707.7	931.1
Operating Segments \| Gas Utilities \| Transportation
Revenue from contracts with customers	43.2	42.7	130.8	131.4
Operating Segments \| Gas Utilities \| Wholesale
Revenue from contracts with customers	0	0	0	0
Operating Segments \| Gas Utilities \| Market - off-system sales
Revenue from contracts with customers	0	0	0.1	0.4
Operating Segments \| Gas Utilities \| Transmission/Other
Revenue from contracts with customers	10.9	9.6	32.1	28.8
Operating Segments \| Gas Utilities \| Other revenues
Revenue	2.1	1.2	13.5	12.2
Operating Segments \| Gas Utilities \| Services transferred at a point in time
Revenue from contracts with customers	0	0	0	0
Operating Segments \| Gas Utilities \| Services transferred over time
Revenue from contracts with customers	$ 171.5	$ 173.1	$ 870.7	$ 1,091.7

Financing_ Short-Term Debt (Add

Financing: Short-Term Debt (Additional Information) (Details) - Revolving Credit Facility $ in Millions	May 31, 2024 USD ($) CreditExtension
Short-Term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 750
Number Of One-Year Extension Options \| CreditExtension	2
Debt Instrument, Term	1 year
Maximum amount outstanding (based on daily outstanding balances)	$ 1,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.175%
Base Rate
Short-Term Debt [Line Items]
Weighted average interest rates	0.125%
Secured Overnight Financing Rate (SOFR)
Short-Term Debt [Line Items]
Weighted average interest rates	1.125%
Letter of Credit
Short-Term Debt [Line Items]
Weighted average interest rates	1.125%

Financing - Schedule of Short-t

Financing - Schedule of Short-term Debt and Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Short-Term Debt [Line Items]
Amount outstanding	$ 17.5		$ 0
Revolving Credit Facility \| Commercial Paper
Short-Term Debt [Line Items]
Amount outstanding	17.5		0
Letters of Credit	3.5		3.7
Available capacity	$ 729		$ 746.3
Weighted average interest rates	4.93%
Maximum amount outstanding (based on daily outstanding balances)	$ 25.8	$ 548.7
Average amount outstanding (based on daily outstanding balances)	$ 0.6	$ 109.2
Weighted average interest rates	5.15%	4.91%

Financing_ Long-term Debt (Addi

Financing: Long-term Debt (Additional Information) (Details) - USD ($) $ in Millions			9 Months Ended
	Aug. 23, 2024	May 16, 2024	Sep. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Repayment of long term debt			$ 600	$ 0
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] \| Senior Unsecured Notes Due 2035 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		$ 450
Stated interest rate (percent)		6%
Less unamortized deferred financing costs		$ 5.2
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] \| Senior Unsecured Notes Due 2024 [Member]
Debt Instrument [Line Items]
Stated interest rate (percent)	1.04%
Repayment of long term debt	$ 600

Financing_ Debt Covenants (Addi

Financing: Debt Covenants (Additional Information) (Details)	Sep. 30, 2024
Line of Credit Facility [Line Items]
Consolidated indebtedness to capitalization ratio	0.55
Maximum
Line of Credit Facility [Line Items]
Consolidated indebtedness to capitalization ratio	0.65
Wyoming Electric
Line of Credit Facility [Line Items]
Consolidated indebtedness to capitalization ratio	0.52
Wyoming Electric \| Maximum
Line of Credit Facility [Line Items]
Consolidated indebtedness to capitalization ratio	0.6

Financing_ At-the-Market Equity

Financing: At-the-Market Equity Offering Program (Details) - Common Stock - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Proceeds, (net of issuance costs)	$ 108.6	$ 52.8	$ 181.6	$ 107.7
Average price per share	$ 56.84	$ 57.33	$ 55.63	$ 60.02
Number of shares issued	1.9	0.9	3.3	1.8
Payments of Stock Issuance Costs	$ (1.1)	$ (0.5)	$ (1.8)	$ (1.1)
August 4, 2020 ATM Program
Proceeds, (net of issuance costs)	$ 0	$ 0	$ 0	$ 48.5
Number of shares issued	0	0	0	0.8
Payments of Stock Issuance Costs	$ 0	$ 0	$ 0	$ (0.5)
June 16, 2023 ATM Program
Proceeds, (net of issuance costs)	$ 108.6	$ 52.8	$ 181.6	$ 59.2
Number of shares issued	1.9	0.9	3.3	1
Payments of Stock Issuance Costs	$ (1.1)	$ (0.5)	$ (1.8)	$ (0.6)

Earnings Per Share - Earnings P

Earnings Per Share - Earnings Per Share Reconciliation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Net Income (Loss)	$ 24.4	$ 45.4	$ 175	$ 182.5
Weighted average shares - Basic (in shares)	70.5	67.3	69.2	66.7
Dilutive effect of equity compensation	0.1	0.1	0.1	0
Weighted average shares - diluted (in shares)	70.6	67.4	69.3	66.7
Net income available for common stock, per share - Diluted	$ 0.35	$ 0.67	$ 2.52	$ 2.74

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares excluded from computation of earnings per share	0	0.1	0	0
Share-Based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares excluded from computation of earnings per share	0	0.1	0	0
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares excluded from computation of earnings per share	0	0	0	0

Risk Management and Derivativ_3

Risk Management and Derivatives: Utilities (Details) $ in Millions		Sep. 30, 2024 USD ($) MMBTU	Dec. 31, 2023 MMBTU
Derivative [Line Items]
Credit Risk Derivative Liabilities, at Fair Value \| $		$ 0.5
Natural Gas, Distribution \| Cash Flow Hedging
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		2,276,000
Natural Gas, Distribution \| Natural gas futures purchased
Derivative [Line Items]
Derivative, Remaining Maturity	[1]	6 months	3 months
Natural Gas, Distribution \| Natural gas futures purchased \| Long
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		1,800,000	650,000
Natural Gas, Distribution \| Natural gas options purchased, net
Derivative [Line Items]
Derivative, Remaining Maturity	[1]	6 months	3 months
Natural Gas, Distribution \| Natural gas options purchased, net \| Long
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		7,680,000	2,850,000
Natural Gas, Distribution \| Natural gas basis swaps purchased
Derivative [Line Items]
Derivative, Remaining Maturity	[1]	6 months	3 months
Natural Gas, Distribution \| Natural gas basis swaps purchased \| Long
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		1,800,000	1,050,000
Natural Gas, Distribution \| Natural gas over-the-counter swaps, net
Derivative [Line Items]
Derivative, Remaining Maturity	[1]	22 months	21 months	[2]
Natural Gas, Distribution \| Natural gas over-the-counter swaps, net \| Long
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	[2]	4,890,000	3,890,000
Natural Gas, Distribution \| Natural gas physical contracts, net
Derivative [Line Items]
Derivative, Remaining Maturity	[1]	6 months	10 months	[3]
Natural Gas, Distribution \| Natural gas physical contracts, net \| Long
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	[3]	32,240,665	12,582,415

[1] Term reflects the maximum forward period hedged. As of September 30, 2024 , 2,276,000 MMBtus of natural gas over-the-counter swaps purchases were designated as cash flow hedges. Volumes exclude derivative contracts that qualify for the normal purchases and normal sales exception permitted by GAAP.

Risk Management and Derivativ_4

Risk Management and Derivatives: Derivatives by Balance Sheet Classification (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ (0.6)	$ (2.9)
Commodity Contract \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(4)	(3.9)
Other assets, non-current \| Commodity Contract \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0	(0.2)
Derivative liabilities, current \| Commodity Contract \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(0.6)	(2.7)
Derivative liabilities, current \| Commodity Contract \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(3.9)	(3.8)
Other deferred credits and other liabilities \| Commodity Contract \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ (0.1)	$ (0.1)

Risk Management and Derivativ_5

Risk Management and Derivatives: Cash Flow Hedges (Details) - Cash Flow Hedging - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Interest rate swaps
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			$ 2.9
Designated as Hedging Instrument
Derivative [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 0.9	$ 0.5	5.3	$ 3.4
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (0.8)	$ (0.7)	$ (5.4)	$ (4.6)
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest
Designated as Hedging Instrument \| Interest rate swaps
Derivative [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 0.8	$ 0.7	$ 2.2	$ 2.1
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	$ (0.8)	$ (0.7)	$ (2.2)	$ (2.1)
Derivative Instrument, Loss Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest Costs Incurred	Interest Costs Incurred	Interest Costs Incurred	Interest Costs Incurred
Designated as Hedging Instrument \| Commodity Contract
Derivative [Line Items]
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 0.1	$ (0.2)	$ 3.1	$ 1.3
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	$ 0	$ 0	$ (3.2)	$ (2.5)
Derivative Instrument, Gain Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold

Risk Management and Derivativ_6

Risk Management and Derivatives: Derivatives Not Designated as Hedge Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Derivative [Line Items]
Regulatory assets	$ 432.2		$ 432.2		$ 480.1
Regulatory liabilities	557		557		566.6
Gas price derivatives
Derivative [Line Items]
Regulatory assets	3.2		3.2		$ 5.1
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (0.3)	$ 0.3	$ 0.4	$ (2.4)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold
Not Designated as Hedging Instrument \| Natural Gas
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (0.3)	$ 0.3	$ 0.4	$ (2.4)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold

Fair Value Measurements_ Schedu

Fair Value Measurements: Schedule of Fair Values (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Derivative Liability, Current	Derivative Liability, Current
Contract Subject to Master Netting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 5.6	$ 1.9
Derivative Liability, Fair Value, Gross Liability	1.1	3.3
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(5.6)	(1.9)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(1.1)	(3.3)
Fair Value, Measurements, Recurring \| Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	0	0
Derivative, Liabilities, Fair Value Disclosure	4.6	6.8
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	0	0
Derivative, Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	5.6	1.9
Derivative, Liabilities, Fair Value Disclosure	5.7	10.1
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	0	0
Derivative, Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring \| Gas Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(5.6)	(1.9)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(1.1)	(3.3)
Fair Value, Measurements, Recurring \| Gas Utilities \| Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	0	0
Derivative, Liabilities, Fair Value Disclosure	4.6	6.8
Fair Value, Measurements, Recurring \| Gas Utilities \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	0	0
Derivative, Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring \| Gas Utilities \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	5.6	1.9
Derivative, Liabilities, Fair Value Disclosure	5.7	10.1
Fair Value, Measurements, Recurring \| Gas Utilities \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value Disclosure	0	0
Derivative, Liabilities, Fair Value Disclosure	$ 0	$ 0

Fair Value Measurements_ Other

Fair Value Measurements: Other Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, including current maturities	$ 4,248.8	$ 4,401.2
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, including current maturities	$ 4,198.7	$ 4,215.6

Other Comprehensive Income_ Rec

Other Comprehensive Income: Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense	$ 50.6			$ 44.5			$ 144.8	$ 131.8
Fuel, purchased power and cost of natural gas sold	94.5			102.2			518.2	749.8
Operations and maintenance	145.6			125.7			420.8	412.5
Income tax expense	(2.9)			(7.4)			(23.6)	(16)
Net income	26.4	$ 24.7	$ 131.6	48.8	$ 26.6	$ 117.4	182.6	192.7
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income	(0.6)			(0.6)			(4.3)	(3.6)
Cash Flow Hedging \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	(0.8)			(0.7)			(5.4)	(4.6)
Income tax expense	0.2			0.1			1.2	1.1
Net income	(0.6)			(0.6)			(4.2)	(3.5)
Cash Flow Hedging \| Reclassification out of Accumulated Other Comprehensive Income \| Interest Rate Swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense	(0.8)			(0.7)			(2.2)	(2.1)
Cash Flow Hedging \| Reclassification out of Accumulated Other Comprehensive Income \| Commodity Contract
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Fuel, purchased power and cost of natural gas sold	0			0			(3.2)	(2.5)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Operations and maintenance	0			0			(0.1)	(0.1)
Accumulated Defined Benefit Plans Adjustment \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	0			0			(0.1)	(0.1)
Income tax expense	0			0			0	0
Net income	$ 0			$ 0			$ (0.1)	$ (0.1)

Other Comprehensive Income_ Acc

Other Comprehensive Income: Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	$ (14.8)	$ (15.6)
Other comprehensive income (loss), before reclassifications	(0.1)	(0.9)
Amounts reclassified from AOCI	4.3	3.6
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(10.6)	(12.9)
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(6.2)	(6.1)
Other comprehensive income (loss), before reclassifications	0	0
Amounts reclassified from AOCI	0.1	0.1
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(6.1)	(6)
Interest Rate Swap \| Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(6.1)	(8.3)
Other comprehensive income (loss), before reclassifications	0	0
Amounts reclassified from AOCI	1.7	1.7
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(4.4)	(6.6)
Commodity Contract \| Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(2.5)	(1.2)
Other comprehensive income (loss), before reclassifications	(0.1)	(0.9)
Amounts reclassified from AOCI	2.5	1.8
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	$ (0.1)	$ (0.3)

Employee Benefit Plans_ Compone

Employee Benefit Plans: Components of Net Periodic Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 0.6	$ 0.6	$ 1.7	$ 1.8
Interest cost	4.1	4.4	12.3	13.1
Expected return on plan assets	(4.5)	(4.7)	(13.4)	(14)
Net amortization of prior service costs	0	0	(0.1)	0
Recognized net actuarial loss	0.5	0.5	1.5	1.5
Net periodic expense	0.7	0.8	2	2.4
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1.3	(0.1)	2.9	1.6
Interest cost	0.4	0.4	1.1	1.1
Expected return on plan assets	0	0	0	0
Net amortization of prior service costs	0	0	0	0
Recognized net actuarial loss	0	0	0	0
Net periodic expense	1.7	0.3	4	2.7
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.4	0.4	1.2	1.1
Interest cost	0.6	0.6	1.8	1.8
Expected return on plan assets	(0.1)	(0.1)	(0.2)	(0.1)
Net amortization of prior service costs	0.1	0	0.1	0
Recognized net actuarial loss	0	0	0	0
Net periodic expense	$ 1	$ 0.9	$ 2.9	$ 2.8

Employee Benefit Plans_ Plan Co

Employee Benefit Plans: Plan Contributions (Details) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated Future Employer Contributions in Next Fiscal Year	$ 1.8
Payment for Pension Benefits	2.3
Estimated Future Employer Contributions in Current Fiscal Year	0
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Estimated Future Employer Contributions in Next Fiscal Year	4.4
Payment for Pension Benefits	3.5
Estimated Future Employer Contributions in Current Fiscal Year	1.2
Supplemental Non-Qualified Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated Future Employer Contributions in Next Fiscal Year	2.8
Payment for Pension Benefits	1.8
Estimated Future Employer Contributions in Current Fiscal Year	$ 0.6

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Jun. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Line Items]
Income tax (expense)		$ (2.9)	$ (7.4)	$ (23.6)	$ (16)
Effective Tax Rate		10%	13.10%	11.40%	7.60%
Transfers of production tax credits to third party	$ 16.9
Nebraska
Income Tax Disclosure [Line Items]
State income tax expense (benefit)					$ 8.2

Business Segment Information -

Business Segment Information - Additional Information (Details)	9 Months Ended
	Sep. 30, 2024 Segment
Segment Reporting Information, Additional Information [Abstract]
Number of operating segments	2

Business Segment Information_ I

Business Segment Information: Information Relating to Segments Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information
Revenue	$ 401.6	$ 407.1	$ 1,530.6	$ 1,739.6
Operating income	75.8	97.8	339.8	336.2
Capital expenditures	185	165.1	565.8	420.6
Corporate, Non-Segment
Segment Reporting Information
Operating income	(0.2)	(0.6)	(0.8)	(2.2)
Capital expenditures	6	1.3	10.8	4.1
Operating Segments \| Electric Utilities
Segment Reporting Information
Revenue	232.5	237.3	659.8	649.1
Operating income	65.1	83	176	190.7
Capital expenditures	61.2	55.7	246.8	155.6
Operating Segments \| Gas Utilities
Segment Reporting Information
Revenue	173.6	174.3	884.2	1,103.9
Operating income	10.9	15.4	164.6	147.7
Capital expenditures	117.8	108.1	308.2	260.9
External Revenues
Segment Reporting Information
Revenue	401.6	407.1	1,530.6	1,739.6
External Revenues \| Operating Segments \| Electric Utilities
Segment Reporting Information
Revenue	229.6	234.5	651	640.6
External Revenues \| Operating Segments \| Gas Utilities
Segment Reporting Information
Revenue	172	172.6	879.6	1,099
Inter-segment Revenues \| Corporate, Non-Segment
Segment Reporting Information
Revenue	(4.5)	(4.5)	(13.4)	(13.4)
Inter-segment Revenues \| Operating Segments \| Electric Utilities
Segment Reporting Information
Revenue	2.9	2.8	8.8	8.5
Inter-segment Revenues \| Operating Segments \| Gas Utilities
Segment Reporting Information
Revenue	$ 1.6	$ 1.7	$ 4.6	$ 4.9

Selected Balance Sheet Inform_3

Selected Balance Sheet Information: Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Selected Balance Sheet Information [Abstract]
Billed Accounts Receivable	$ 136.9	$ 198.5
Unbilled Revenue	69.9	154
Less: Allowance for Credit Losses	(1.4)	(2.2)	$ (1.8)	$ (3)
Account Receivable, net	$ 205.4	$ 350.3

Selected Balance Sheet Inform_4

Selected Balance Sheet Information: Changes to Allowance for Credit Losses (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Selected Balance Sheet Information [Abstract]
Balance at Beginning of Year	$ 2.2	$ 3
Additions Charged to Costs and Expenses	4	7.2
Recoveries and Other Additions	2.8	2.4
Write-offs and Other Deductions	(7.6)	(10.8)
Balance at End of Year	$ 1.4	$ 1.8

Selected Balance Sheet Inform_5

Selected Balance Sheet Information: Materials, Supplies, and Fuel Schedule (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Selected Balance Sheet Information [Abstract]
Materials and supplies	$ 103.9	$ 105.9
Fuel - Electric Utilities	7.6	7.7
Natural gas in storage	43.9	47.3
Total materials, supplies and fuel	$ 155.4	$ 160.9

Selected Balance Sheet Inform_6

Selected Balance Sheet Information: Accrued Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Selected Balance Sheet Information [Abstract]
Accrued employee compensation, benefits and withholdings	$ 78.8	$ 74.8
Accrued property taxes	47.7	52.7
Customer deposits and prepayments	59.2	76
Accrued interest	60.4	46.3
Other (none of which is individually significant)	45.6	43.5
Total accrued liabilities	$ 291.7	$ 293.3