Public Service Co Of Colorado 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 07, 2020
Cover [Abstract]
Entity Registrant Name	PUBLIC SERVICE CO OF COLORADO
Entity Central Index Key	0000081018
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity Incorporation, State or Country Code	CO
Entity File Number	001-03280
Entity Tax Identification Number	84-0296600
Entity Address, Address Line One	1800 Larimer, Suite 1100
Entity Address, City or Town	Denver
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80202
City Area Code	(303)
Local Phone Number	571-7511
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		100

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2018		100
Beginning balance at Dec. 31, 2018	$ 6,298,200	$ 0	$ 4,340,500	$ 1,983,200	$ (25,500)
Increase (Decrease) in Stockholder's Equity
Net income	138,800			138,800
Other comprehensive income	300				300
Dividends declared to parent	(98,800)			(98,800)
Contribution of capital by parent	50,000		50,000
Balance (in shares) at Mar. 31, 2019		100
Ending balance at Mar. 31, 2019	$ 6,388,500	$ 0	4,390,500	2,023,200	(25,200)
Balance (in shares) at Dec. 31, 2019	100	100
Beginning balance at Dec. 31, 2019	$ 6,996,200	$ 0	4,939,400	2,083,400	(26,600)
Increase (Decrease) in Stockholder's Equity
Net income	128,700			128,700
Other comprehensive income	300				300
Dividends declared to parent	(102,500)			(102,500)
Contribution of capital by parent	$ 50,000		50,000
Balance (in shares) at Mar. 31, 2020	100	100
Increase (Decrease) in Stockholder's Equity
Adoption of ASC Topic 326	$ (700)			(700)
Ending balance at Mar. 31, 2020	$ 7,072,000	$ 0	$ 4,989,400	$ 2,108,900	$ (26,300)

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating revenues
Electric	$ 711.8	$ 741.5
Gas	331.5	469.1
Steam and other	13.4	12.4
Total operating revenues	1,056.7	1,223
Operating expenses
Electric fuel and purchased power	270.8	304.2
Cost of natural gas sold and transported	137.6	272.5
Cost of sales — steam and other	3	4.4
Operating and maintenance expenses	204.5	199.3
Demand side management expenses	35.6	32.1
Depreciation and amortization	156.4	146.9
Taxes (other than income taxes)	53.2	53.7
Total operating expenses	861.1	1,013.1
Operating income	195.6	209.9
Other (expense) income, net	(1.8)	1
Allowance for funds used during construction — equity	8.6	4.1
Interest charges and financing costs
Interest charges — includes other financing costs of $1.7, and $1.6, respectively	60.1	59.5
Allowance for funds used during construction — debt	(3.8)	(2.4)
Total interest charges and financing costs	56.3	57.1
Income before income taxes	146.1	157.9
Income tax expense	17.4	19.1
Net income	$ 128.7	$ 138.8

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest charges and financing costs
Other financing costs	$ 1.7	$ 1.6

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Comprehensive income:
Net income	$ 128.7	$ 138.8
Derivative instruments:
Reclassification of loss to net income, net of tax of $0.1	0.3	0.3
Total other comprehensive income	0.3	0.3
Total comprehensive income	$ 129	$ 139.1

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative instruments:
Reclassification of losses (gains) to net income, tax	$ 0.1	$ 0.1

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net income	$ 128.7	$ 138.8
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	157.7	148.2
Deferred income taxes	5.9	(1.2)
Amortization of investment tax credits	(0.6)	(0.6)
Allowance for equity funds used during construction	(8.6)	(4.1)
Net realized and unrealized hedging and derivative transactions	1.7	(2.6)
Changes in operating assets and liabilities:
Accounts receivable	7.8	(54.7)
Accrued unbilled revenues	75.3	32.2
Inventories	30.4	33.5
Prepayments and other	8.3	(9.3)
Accounts payable	(94.6)	(45.7)
Net regulatory assets and liabilities	42.7	93.2
Other current liabilities	32.6	42.6
Pension and other employee benefit obligations	(48.4)	(43.7)
Other, net	(5.9)	1.9
Net cash provided by operating activities	333	328.5
Investing activities
Utility capital/construction expenditures	(458.4)	(282.9)
Investments in utility money pool arrangement	0	(131)
Repayments from utility money pool arrangement	0	131
Net cash used in investing activities	(458.4)	(282.9)
Financing activities
Repayments of short-term borrowings, net	0	(68)
Borrowings under utility money pool arrangement	446	0
Repayments under utility money pool arrangement	(289)	0
Proceeds from issuance of long-term debt	0	392.6
Repayments of long-term debt	0	400
Capital contributions from parent	83.4	112.2
Dividends paid to parent	(111.5)	(91.6)
Other, net	(0.3)	0
Net cash provided by financing activities	128.6	(54.8)
Net change in cash, cash equivalents and restricted cash	3.2	(9.2)
Cash, cash equivalents and restricted cash at beginning of period	11.4	33.4
Cash, cash equivalents and restricted cash at end of period	14.6	24.2
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(72.6)	(65.3)
Cash paid for income taxes, net	1.9	(10.7)
Supplemental disclosure of non-cash investing and financing transactions:
Accrued property, plant and equipment additions	132.1	85.1
Inventory transfers to property, plant and equipment	8.1	6.9
Operating lease right-of-use assets	0	652.8
Allowance for equity funds used during construction	$ 8.6	$ 4.1

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 14.6	$ 11.4
Accounts receivable, net	314.9	303.9
Accounts receivable from affiliates	0.7	52.7
Accrued unbilled revenues	217.7	293.9
Inventories	153.5	192
Regulatory assets	76.1	64
Derivative instruments	5	7.2
Prepayments and other	51.4	55.9
Total current assets	833.9	981
Property, plant and equipment, net	16,629.6	16,155
Other assets
Regulatory assets	1,038.8	1,038.1
Operating lease right-of-use assets	553.4	574
Other	257.9	259.4
Total other assets	1,850.1	1,871.5
Total assets	19,313.6	19,007.5
Current liabilities
Current portion of long-term debt	400	400
Borrowings under utility money pool arrangement	196	39
Accounts payable	374.2	573.3
Accounts payable to affiliates	49.9	43.9
Regulatory liabilities	104.3	69.2
Taxes accrued	268	202.1
Accrued interest	35.3	53.4
Dividends payable to parent	102.5	111.5
Derivative instruments	8.7	8.7
Operating lease liabilities	86.9	85.8
Other	82.6	98.8
Total current liabilities	1,708.4	1,685.7
Deferred credits and other liabilities
Deferred income taxes	1,867.8	1,850.8
Deferred investment tax credits	22.2	22.8
Regulatory liabilities	2,302.7	2,036.8
Asset retirement obligations	327.6	324
Derivative instruments	48.2	52.5
Customer advances	173	173.6
Pension and employee benefit obligations	163.1	211.9
Operating lease liabilities	495.6	517.6
Other	147.3	150.9
Total deferred credits and other liabilities	5,547.5	5,340.9
Capitalization
Long-term debt	4,985.7	4,984.7
Common stock — 100 shares authorized at $0.01 par value; 100 shares outstanding at March 31, 2020 and Dec. 31, 2019, respectively	0	0
Additional paid in capital	4,989.4	4,939.4
Retained earnings	2,108.9	2,083.4
Accumulated other comprehensive loss	(26.3)	(26.6)
Total common stockholder’s equity	7,072	6,996.2
Total liabilities and equity	$ 19,313.6	$ 19,007.5

CONSOLIDATED BALANCE SHEETS (_2

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Capitalization, Long-term Debt and Equity [Abstract]
Common stock, shares authorized (in shares)	100	100
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares outstanding (in shares)	100	100

Management's Opinion

Management's Opinion	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Opinion	In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments necessary to present fairly, in accordance with U.S. GAAP, the financial position of PSCo and its subsidiaries as of March 31, 2020 and Dec. 31, 2019 ; the results of its operations, including the components of net income, comprehensive income and changes in stockholders’ equity for the three months ended March 31, 2020 and 2019 ; and its cash flows for the three months ended March 31, 2020 and 2019 . All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after March 31, 2020 , up to the date of issuance of these consolidated financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation. The Dec. 31, 2019 , balance sheet information has been derived from the audited 2019 consolidated financial statements included in the PSCo Annual Report on Form 10-K for the year ended Dec. 31, 2019 . These notes to the consolidated financial statements have been prepared pursuant to the rules and regulations of the SEC for Quarterly Reports on Form 10-Q. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP on an annual basis have been condensed or omitted pursuant to such rules and regulations. For further information, refer to the consolidated financial statements and notes thereto, included in the PSCo Annual Report on Form 10-K for the year ended Dec. 31, 2019 , filed with the SEC on Feb. 21, 2020. Due to the seasonality of PSCo’s electric and natural gas sales, interim results are not necessarily an appropriate base from which to project annual results.

Selected Balance Sheet Data

Selected Balance Sheet Data	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 337.4 $ 324.9 Less allowance for bad debts (22.5 ) (21.0 ) Accounts receivable, net $ 314.9 $ 303.9 (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 62.5 $ 62.6 Fuel 64.4 77.1 Natural gas 26.6 52.3 Total inventories $ 153.5 $ 192.0 (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 14,449.3 $ 14,361.9 Natural gas plant 4,703.8 4,631.4 Common and other property 1,132.4 1,113.5 Plant to be retired (a) 216.5 259.9 Construction work in progress 1,061.7 912.7 Total property, plant and equipment 21,563.7 21,279.4 Less accumulated depreciation (4,934.1 ) (5,124.4 ) Property, plant and equipment, net $ 16,629.6 $ 16,155.0 (a) In 2018, the CPUC approved early retirement of PSCo’s Comanche Units 1 and 2 in approximately 2022 and 2025, respectively. PSCo also expects Craig Unit 1 to be retired early in 2025. Amounts are presented net of accumulated depreciation.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	The significant accounting policies set forth in Note 1 to the consolidated financial statements in the PSCo Annual Report on Form 10-K for the year ended Dec. 31, 2019 , appropriately represent, in all material respects, the current status of accounting policies and are incorporated herein by reference.

Accounting Pronouncements

Accounting Pronouncements	3 Months Ended
	Mar. 31, 2020
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Accounting Pronouncements	Recently Adopted Credit Losses — In 2016, the FASB issued Financial Instruments - Credit Losses, Topic 326 (ASC Topic 326), which changes how entities account for losses on receivables and certain other assets. The guidance requires use of a current expected credit loss model, which may result in earlier recognition of credit losses than under previous accounting standards. PSCo implemented the guidance using a modified-retrospective approach, recognizing a cumulative effect charge of $0.7 million

Borrowings and Other Financing

Borrowings and Other Financing Instruments	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Borrowings and Other Financing Instruments	Short-Term Borrowings PSCo meets its short-term liquidity requirements primarily through the issuance of commercial paper and borrowings under its credit facility and the money pool. Money Pool — Xcel Energy Inc. and its utility subsidiaries have established a money pool arrangement that allows for short-term investments in and borrowings between the utility subsidiaries. Xcel Energy Inc. may make investments in the utility subsidiaries at market-based interest rates; however, the money pool arrangement does not allow the utility subsidiaries to make investments in Xcel Energy Inc. Money pool borrowings for PSCo were as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end 196 39 Average amount outstanding 34 7 Maximum amount outstanding 208 50 Weighted average interest rate, computed on a daily basis 1.38 % 2.29 % Weighted average interest rate at period end 1.15 1.63 % Commercial Paper — Commercial paper outstanding for PSCo was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 700 $ 700 Amount outstanding at period end — — Average amount outstanding 90 154 Maximum amount outstanding 230 432 Weighted average interest rate, computed on a daily basis 1.95 % 2.67 % Weighted average interest rate at period end N/A N/A Letters of Credit — PSCo uses letters of credit, generally with terms of one year , to provide financial guarantees for certain operating obligations. There were $8 million and $9 million of letters of credit outstanding under the credit facility at March 31, 2020 and Dec. 31, 2019 , respectively. The contract amounts of these letters of credit approximate their fair value and are subject to fees. Revolving Credit Facility — In order to use its commercial paper program to fulfill short‑term funding needs, PSCo must have a revolving credit facility in place at least equal to the amount of its commercial paper borrowing limit and cannot issue commercial paper in an aggregate amount exceeding available capacity under this credit facility. The credit facility provides short-term financing in the form of notes payable to banks, letters of credit and back-up support for commercial paper borrowings. PSCo has the right to request an extension of the revolving credit facility termination date for two additional one year periods. All extension requests are subject to majority bank group approval. At March 31, 2020 , PSCo had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 700 $ 8 $ 692 (a) This credit facility expires in June 2024 . (b) Includes outstanding commercial paper and letters of credit. All credit facility bank borrowings, outstanding letters of credit and outstanding commercial paper reduce the available capacity under the credit facility. PSCo had no direct advances on the credit facility outstanding at March 31, 2020 and Dec. 31, 2019 .

Revenues

Revenues	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenues	Revenue is classified by the type of goods/services rendered and market/customer type. PSCo’s operating revenues consists of the following: Three Months Ended March 31, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 237.5 $ 217.4 $ 3.1 $ 458.0 C&I 352.0 77.8 9.2 439.0 Other 12.2 — — 12.2 Total retail 601.7 295.2 12.3 909.2 Wholesale 47.3 — — 47.3 Transmission 13.4 — — 13.4 Other 14.8 29.8 — 44.6 Total revenue from contracts with customers 677.2 325.0 12.3 1,014.5 Alternative revenue and other 34.6 6.5 1.1 42.2 Total revenues $ 711.8 $ 331.5 $ 13.4 $ 1,056.7 Three Months Ended March 31, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 245.1 $ 311.4 $ 2.5 $ 559.0 C&I 367.9 120.3 8.8 497.0 Other 12.5 — — 12.5 Total retail 625.5 431.7 11.3 1,068.5 Wholesale 57.3 — — 57.3 Transmission 13.4 — — 13.4 Other 11.6 31.6 — 43.2 Total revenue from contracts with customers 707.8 463.3 11.3 1,182.4 Alternative revenue and other 33.7 5.8 1.1 40.6 Total revenues $ 741.5 $ 469.1 $ 12.4 $ 1,223.0

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 7 to the consolidated financial statements included in PSCo’s Annual Report on Form 10-K for the year ended Dec. 31, 2019 , represents, in all material respects, the current status of other income tax matters except to the extent noted below and are incorporated herein by reference. The following table reconciles the difference between the statutory rate and the ETR: Three Months Ended March 31 2020 2019 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 3.7 3.7 (Decreases) increases in tax from: Wind PTCs (8.0 ) (7.5 ) Plant regulatory differences (a) (4.8 ) (3.9 ) Other tax credits, net of NOL & tax credit allowances (0.1 ) (1.2 ) Other (net) 0.1 — Effective income tax rate 11.9 % 12.1 % (a) Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions. Federal Audits — PSCO is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows: Tax Years Expiration 2009 - 2013 September 2020 2014 - 2016 June 2021 In 2015, the IRS commenced an examination of tax years 2012 and 2013. In 2017, the IRS concluded the audit of tax years 2012 and 2013 and proposed an adjustment that would impact Xcel Energy’s NOL and ETR. Xcel Energy filed a protest with the IRS. As of March 31, 2020 , the case has been forwarded to Office of Appeals and Xcel Energy has recognized its best estimate of income tax expense that will result from a final resolution of this issue; however, the outcome and timing of a resolution is unknown. In 2018, the IRS began an audit of tax years 2014 - 2016. As of March 31, 2020 , no adjustments have been proposed. State Audits — PSCo is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of March 31, 2020 , PSCo’s earliest open tax year subject to examination by state taxing authorities under applicable statutes of limitations is 2009. There are currently no state income tax audits in progress. Unrecognized Benefits — Unrecognized tax benefit balance includes permanent tax positions, which if recognized would affect the annual ETR. In addition, the unrecognized tax benefit balance includes temporary tax positions for which ultimate deductibility is highly certain but for which there is uncertainty about the timing of such deductibility. A change in the period of deductibility would not affect the ETR but would accelerate the payment to the taxing authority to an earlier period. Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 7.8 $ 7.4 Unrecognized tax benefit — Temporary tax positions 4.6 4.6 Total unrecognized tax benefit $ 12.4 $ 12.0 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (8.7 ) $ (8.3 ) Net deferred tax liability associated with the unrecognized tax benefit amounts and related NOLs and tax credits carryforwards were $5.4 million and $5.0 million for March 31, 2020 and Dec. 31, 2019 , respectively. As the IRS Appeals and federal audit progress and state audits resume, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $8.7 million in the next 12 months. Payable for interest related to unrecognized tax benefits is partially offset by the interest benefit associated with NOL and tax credit carryforwards. Interest payable related to unrecognized tax benefits: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Payable for interest related to unrecognized tax benefits at beginning of period $ (1.1 ) $ (0.7 ) Interest expense related to unrecognized tax benefits (0.1 ) (0.4 ) Payable for interest related to unrecognized tax benefits at end of period $ (1.2 ) $ (1.1 ) No amounts were accrued for penalties related to unrecognized tax benefits as of March 31, 2020 and Dec. 31, 2019 .

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	Fair Value Measurements Accounting guidance for fair value measurements and disclosures provides a single definition of fair value and requires disclosures about assets and liabilities measured at fair value. A hierarchical framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value is established by this guidance. • Level 1 — Quoted prices are available in active markets for identical assets or liabilities as of the reporting date. The types of assets and liabilities included in Level 1 are highly liquid and actively traded instruments with quoted prices; • Level 2 — Pricing inputs are other than quoted prices in active markets, but are either directly or indirectly observable as of the reporting date. The types of assets and liabilities included in Level 2 are typically either comparable to actively traded securities or contracts, or priced with models using highly observable inputs; and • Level 3 — Significant inputs to pricing have little or no observability as of the reporting date. The types of assets and liabilities included in Level 3 are those valued with models requiring significant management judgment or estimation. Specific valuation methods include: Cash equivalents — The fair values of cash equivalents are generally based on cost plus accrued interest; money market funds are measured using quoted NAV. Interest rate derivatives — The fair values of interest rate derivatives are based on broker quotes that utilize current market interest rate forecasts. Commodity derivatives — The methods used to measure the fair value of commodity derivative forwards and options utilize forward prices and volatilities, as well as pricing adjustments for specific delivery locations and are generally assigned a Level 2 classification. When contractual settlements relate to inactive delivery locations or extend to periods beyond those readily observable on active exchanges or quoted by brokers, the significance of the use of less observable forecasts of forward prices and volatilities on a valuation is evaluated and may result in Level 3 classification. Derivative Instruments Fair Value Measurements PSCo enters into derivative instruments, including forward contracts, futures, swaps and options, for trading purposes and to manage risk in connection with changes in interest rates, utility commodity prices and vehicle fuel prices. Interest Rate Derivatives — PSCo enters into various instruments that effectively fix the interest payments on certain floating rate debt obligations or effectively fix the yield or price on a specified benchmark interest rate for an anticipated debt issuance for a specific period. These derivative instruments are generally designated as cash flow hedges for accounting purposes. At March 31, 2020 , accumulated other comprehensive loss related to interest rate derivatives included $1.2 million of net losses expected to be reclassified into earnings during the next 12 months as the related hedged interest rate transactions impact earnings, including forecasted amounts for unsettled hedges, as applicable. Wholesale and Commodity Trading Risk — PSCo conducts various wholesale and commodity trading activities, including the purchase and sale of electric capacity, energy, energy-related instruments and natural gas-related instruments, including derivatives. PSCo is allowed to conduct these activities within guidelines and limitations as approved by its risk management committee, comprised of management personnel not directly involved in activities governed by this policy. Commodity Derivatives — PSCo enters into derivative instruments to manage variability of future cash flows from changes in commodity prices in its electric and natural gas operations, as well as for trading purposes. This could include the purchase or sale of energy or energy-related products, natural gas to generate electric energy, natural gas for resale and vehicle fuel. PSCo enters into derivative instruments that mitigate commodity price risk on behalf of electric and natural gas customers but may not be designated as qualifying hedging transactions. Changes in the fair value of non-trading commodity derivative instruments are recorded as other comprehensive income or deferred as a regulatory asset or liability. The classification as a regulatory asset or liability is based on commission approved regulatory recovery mechanisms. As of March 31, 2020 , PSCo had no commodity contracts designated as cash flow hedges. PSCo enters into commodity derivative instruments for trading purposes not directly related to commodity price risks associated with serving its electric and natural gas customers. Changes in the fair value of these commodity derivatives are recorded in electric operating revenues, net of amounts credited to customers under margin-sharing mechanisms. Gross notional amounts of commodity forwards and options: (Amounts in Millions) (a)(b) March 31, 2020 Dec. 31, 2019 MWh of electricity 9.4 9.3 MMBtu of natural gas 50.4 32.2 (a) Amounts are not reflective of net positions in the underlying commodities. (b) Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise. Consideration of Credit Risk and Concentrations — PSCo continuously monitors the creditworthiness of the counterparties to its interest rate derivatives and commodity derivative contracts prior to settlement and assesses each counterparty’s ability to perform on the transactions set forth in the contracts. The impact of credit risk was immaterial to the fair value of unsettled commodity derivatives presented in the consolidated balance sheets. PSCo’s most significant concentrations of credit risk with particular entities or industries are contracts with counterparties to its wholesale, trading and non-trading commodity activities. At March 31, 2020 , four of PSCo’s 10 most significant counterparties for these activities, comprising $113.3 million , or 77% , of this credit exposure, had investment grade credit ratings from S&P Global Ratings, Moody’s Investor Services or Fitch Ratings. Five of the 10 most significant counterparties, comprising $20.6 million , or 14% , of this credit exposure, were not rated by these external agencies, but based on PSCo’s internal analysis, had credit quality consistent with investment grade. One of these significant counterparties, comprising $2.3 million , or 1% , of this credit exposure, had credit quality less than investment grade, based on external analysis. Eight of these significant counterparties are independent system operators, municipal or cooperative electric entities, RTOs or other utilities. As of March 31, 2020 , PSCo had no activity for natural gas commodity derivatives that were recognized in regulatory (assets) and liabilities. The impact of derivative activity for Dec. 31, 2019 , is as follows: Pre-Tax Fair Value Gains Recognized During the Period in: (Millions of Dollars) Accumulated Other Regulatory (Assets) and Liabilities Three Months Ended March 31, 2019 Other derivative instruments Natural gas commodity $ — $ 3.3 Total $ — $ 3.3 Pre-Tax Losses Pre-Tax Losses Recognized (Millions of Dollars) Accumulated Regulatory Three Months Ended March 31, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total 0.4 — — Other derivative instruments Commodity trading — — (2.1 ) (b) Natural gas commodity — 3.4 (c) (3.4 ) (c) Total $ — $ 3.4 $ (5.5 ) (a) Amounts are recorded to interest charges. (b) Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate. (c) Amounts for the three months ended March 31, 2020 , included no settlement gain or losses on derivatives entered to mitigate natural gas price risk for electric generation recorded to electric fuel and purchased power, subject to cost-recovery mechanisms and reclassified to a regulatory asset, as appropriate. Remaining derivative settlement losses for the three months ended March 31, 2020 , relate to natural gas operations and are recorded to cost of natural gas sold and transported. These gains and losses are subject to cost-recovery mechanisms and reclassified out of income to a regulatory asset or liability, as appropriate. Pre-Tax (Gains) Losses Pre-Tax Gains (Losses) Recognized (Millions of Dollars) Accumulated Regulatory Assets and Three Months Ended March 31, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total 0.4 — — Other derivative instruments Commodity trading — — 0.9 (b) Natural gas commodity — (1.3 ) (c) (2.0 ) (c) Total $ — $ (1.3 ) $ (1.1 ) (a) Amounts are recorded to interest charges. (b) Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate. (c) Amounts for the three months ended March 31, 2019 , included no settlement gain or losses on derivatives entered to mitigate natural gas price risk for electric generation recorded to electric fuel and purchased power, subject to cost-recovery mechanisms and reclassified to a regulatory asset, as appropriate. Remaining derivative settlement losses for the three months ended March 31, 2019 , relate to natural gas operations and are recorded to cost of natural gas sold and transported. These gains and losses are subject to cost-recovery mechanisms and reclassified out of income to a regulatory asset or liability, as appropriate. PSCo had no derivative instruments designated as fair value hedges during the three months ended March 31, 2020 and 2019 . Credit Related Contingent Features — Contract provisions for derivative instruments that PSCo enters into, including those accounted for as normal purchase-normal sale contracts and therefore not reflected on the consolidated balance sheets, may require the posting of collateral or settlement of the contracts for various reasons, including if PSCo’s credit ratings are downgraded below its investment grade credit rating by any of the major credit rating agencies, or for cross-default contractual provisions if there was a failure under other financing arrangements related to payment terms or other covenants. At March 31, 2020 and Dec. 31, 2019 , there were no derivative instruments in a liability position with such underlying contract provisions. Certain derivative instruments are also subject to contract provisions that contain adequate assurance clauses. These provisions allow counterparties to seek performance assurance, including cash collateral, in the event that PSCo’s ability to fulfill its contractual obligations is reasonably expected to be impaired. PSCo had no collateral posted related to adequate assurance clauses in derivative contracts as of March 31, 2020 and Dec. 31, 2019 . Recurring Fair Value Measurements — PSCo’s derivative assets and liabilities measured at fair value on a recurring basis: March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative assets Other derivative instruments: Commodity trading $ 4.7 $ 14.8 $ 0.6 $ 20.1 $ (15.1 ) $ 5.0 $ 1.9 $ 11.1 $ 0.9 $ 13.9 $ (10.1 ) $ 3.8 Natural gas commodity — — — — — — — 3.4 — 3.4 — 3.4 Total current derivative assets $ 4.7 $ 14.8 $ 0.6 $ 20.1 $ (15.1 ) $ 5.0 $ 1.9 $ 14.5 $ 0.9 $ 17.3 $ (10.1 ) $ 7.2 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 0.3 $ 6.8 $ 0.4 $ 7.5 $ (7.5 ) $ — $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6 ) $ — Total noncurrent derivative assets $ 0.3 $ 6.8 $ 0.4 $ 7.5 $ (7.5 ) $ — $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6 ) $ — March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative liabilities Other derivative instruments: Commodity trading $ 4.1 $ 20.2 $ — $ 24.3 $ (15.6 ) $ 8.7 $ 1.7 $ 16.7 $ — $ 18.4 $ (13.1 ) $ 5.3 Natural gas commodity — — — — — — — 3.4 — 3.4 — 3.4 Total current derivative liabilities $ 4.1 $ 20.2 $ — $ 24.3 $ (15.6 ) $ 8.7 $ 1.7 $ 20.1 $ — $ 21.8 $ (13.1 ) $ 8.7 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 0.3 $ 44.9 $ 15.6 $ 60.8 $ (12.6 ) $ 48.2 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6 ) $ 52.5 Total noncurrent derivative liabilities $ 0.3 $ 44.9 $ 15.6 $ 60.8 $ (12.6 ) $ 48.2 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6 ) $ 52.5 (a) PSCo nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at March 31, 2020 and Dec. 31, 2019 . At both March 31, 2020 and Dec. 31, 2019 , derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $5.6 million and $3.0 million , respectively. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. There were $1.0 million of losses and $0.7 million of gains recognized in earnings for Level 3 commodity trading derivatives in the three months ended March 31, 2020 and 2019 , respectively. PSCo recognizes transfers between levels as of the beginning of each period. There were no transfers of amounts between levels for derivative instruments for the three months ended March 31, 2020 and 2019 . Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: March 31, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 5,385.7 $ 5,891.1 $ 5,384.7 $ 6,039.3 Fair value of PSCo’s long-term debt is estimated based on recent trades and observable spreads from benchmark interest rates for similar securities. Fair value estimates are based on information available to management as of March 31, 2020 and Dec. 31, 2019 , and given the observability of the inputs, fair values presented for long-term debt were assigned as Level 2.

Benefit Plans and Other Postret

Benefit Plans and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost (Credit) Three Months Ended March 31 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 7.6 $ 6.4 $ 0.1 $ 0.1 Interest cost (a) 11.4 12.9 3.2 3.9 Expected return on plan assets (a) (17.6 ) (17.1 ) (4.4 ) (4.7 ) Amortization of prior service credit (a) (0.7 ) (0.8 ) (1.0 ) (1.4 ) Amortization of net loss (a) 7.5 6.3 0.4 0.7 Net periodic benefit cost (credit) 8.2 7.7 (1.7 ) (1.4 ) Credits not recognized due to effects of regulation 0.6 1.9 0.6 0.3 Net benefit cost (credit) recognized for financial reporting $ 8.8 $ 9.6 $ (1.1 ) $ (1.1 ) (a) The components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset. In January 2020, contributions of $150.0 million were made across four of Xcel Energy’s pension plans, of which $50.0 million was attributable to PSCo. Xcel Energy does not expect additional pension contributions during 2020.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	The following include commitments, contingencies and unresolved contingencies that are material to PSCo’s financial position. Legal PSCo is involved in various litigation matters in the ordinary course of business. The assessment of whether a loss is probable or is a reasonable possibility, and whether the loss or a range of loss is estimable, often involves a series of complex judgments about future events. Management maintains accruals for losses probable of being incurred and subject to reasonable estimation. Management is sometimes unable to estimate an amount or range of a reasonably possible loss in certain situations, including but not limited to, when (1) the damages sought are indeterminate, (2) the proceedings are in the early stages, or (3) the matters involve novel or unsettled legal theories. In such cases, there is considerable uncertainty regarding the timing or ultimate resolution of such matters, including a possible eventual loss. For current proceedings not specifically reported herein, management does not anticipate that the ultimate liabilities, if any, would have a material effect on PSCo’s financial statements. Unless otherwise required by GAAP, legal fees are expensed as incurred. Gas Trading Litigation — e prime is a wholly owned subsidiary of Xcel Energy. e prime was in the business of natural gas trading and marketing but has not engaged in natural gas trading or marketing activities since 2003. Multiple lawsuits seeking monetary damages were commenced against e prime and its affiliates, including Xcel Energy, between 2003 and 2009 alleging fraud and anticompetitive activities in conspiring to restrain the trade of natural gas and manipulate natural gas prices. Cases were all consolidated in the U.S. District Court in Nevada. Two cases remain active which include an MDL matter consisting of a Colorado purported class (Breckenridge) and a Wisconsin purported class (Arandell Corp.). Breckenridge/Colorado — In February 2019, the MDL panel remanded Breckenridge back to the U.S. District Court in Colorado. Arandell Corp. — In February 2019, the case was remanded back to the U.S. District Court in Wisconsin. Plaintiffs are seeking class certification. It is uncertain when the court will rule on this issue. Xcel Energy has concluded that a loss is remote for both remaining lawsuits. Environmental MGP, Landfill and Disposal Sites PSCo is cooperating with the City of Denver on an environmental investigation of the Rice Yards Site in Denver, Colorado, which had various historic industrial uses by multiple parties, including railroad, maintenance shop, scrap metal yard and MGP operations. The area is being redeveloped into residential and commercial mixed uses, and PSCo is in discussions with the current property owner regarding legal claims related to the Rice Yards Site. In addition to the Rice Yards Site, PSCo is currently investigating, remediating or performing post-closure actions at two other MGP, landfill or other disposal sites across its service territory. PSCo has recognized its best estimate of costs/liabilities that will result from final resolution of these issues, however, the outcome and timing is unknown. In addition, there may be insurance recovery and/or recovery from other potentially responsible parties, offsetting a portion of costs incurred. Environmental Requirements — Water and Waste Coal Ash Regulation — PSCo’s operations are subject to federal and state regulations that impose requirements for handling, storage, treatment and disposal of solid waste. Under the CCR Rule, utilities are required to complete groundwater sampling around their CCR landfills and surface impoundments. Currently, PSCo has six regulated ash units in operation. PSCo is conducting groundwater sampling and where appropriate, implementing assessment of corrective measures at certain CCR landfills and surface impoundments. In 2019, groundwater monitoring consistent with the CCR Rule was conducted. Statistically significant increases above background concentrations were detected at four locations. Subsequently, assessment monitoring samples were collected, and PSCo is evaluating options for corrective action at two locations. Until PSCo completes its assessment, it is uncertain what impact, if any, there will be on the operations, financial condition or cash flows. In August 2018, the United States Court of Appeals for the District of Columbia Circuit ruled that the EPA cannot allow utilities to continue to use unlined impoundments (including clay lined impoundments) for the storage or disposal of coal ash. In November 2019, the EPA proposed rules in response to this decision that, if finalized in their current form, may require PSCo to expedite closure of one coal ash impoundment that was not previously required to close. PSCo is pursuing options through comment on the proposed rules or some other means to allow continued operation of this impoundment until the generating units are retired in 2025, at which time the impoundment would be closed. Closure costs for existing impoundments are included in the calculation of the asset retirement obligation liability. VIEs Under certain PPAs, PSCo purchases power from IPPs for which PSCo is required to reimburse fuel costs, or to participate in tolling arrangements under which PSCo procures the natural gas required to produce the energy that it purchases. These specific PPAs create a variable interest in the IPP. PSCo had approximately 1,442 MW of capacity under long-term PPAs at March 31, 2020 and Dec. 31, 2019 , with entities that have been determined to be VIEs. PSCo concluded that these entities are not required to be consolidated in its consolidated financial statements because it does not have the power to direct the activities that most significantly impact the entities’ economic performance. Agreements have expiration dates through 2032 .

Other Comprehensive Income

Other Comprehensive Income	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Other Comprehensive Income	Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2020 and 2019 : Three Months Ended March 31, 2020 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (24.1 ) $ (2.5 ) $ (26.6 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 Accumulated other comprehensive loss at March 31 $ (23.8 ) $ (2.5 ) $ (26.3 ) (a) Included in interest charges. Three Months Ended March 31, 2019 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (25.3 ) $ (0.2 ) $ (25.5 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 Accumulated other comprehensive loss at March 31 $ (25.0 ) $ (0.2 ) $ (25.2 ) (a) Included in interest charges.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Segment Information	PSCo evaluates performance based on profit or loss generated from the product or service provided. These segments are managed separately because the revenue streams are dependent upon regulated rate recovery, which is separately determined for each segment. PSCo has the following reportable segments: • Regulated Electric — The regulated electric utility segment generates electricity which is transmitted and distributed in Colorado. This segment includes sales for resale and provides wholesale transmission service to various entities in the United States. Regulated electric utility also includes PSCo’s wholesale commodity and trading operations; and • Regulated Natural Gas — The regulated natural gas utility segment transports, stores and distributes natural gas in portions of Colorado. PSCo presents Other, which includes operating segments, with revenues below the necessary quantitative thresholds. Those operating segments primarily include steam revenue, appliance repair services and nonutility real estate activities. Asset and capital expenditure information is not provided for PSCo’s reportable segments because as an integrated electric and natural gas utility, PSCo operates significant assets that are not dedicated to a specific business segment and reporting assets and capital expenditures by business segment would require arbitrary and potentially misleading allocations, which may not necessarily reflect the assets that would be required for the operation of the business segments on a stand-alone basis. To report income from operations for regulated electric and regulated natural gas utility segments, the majority of costs are directly assigned to each segment. However, some costs, such as common depreciation, common O&M expenses and interest expense are allocated based on cost causation allocators. A general allocator is used for certain general and administrative expenses, including office supplies, rent, property insurance and general advertising. PSCo’s segment information for the three months ended March 31 : (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 711.8 $ 741.5 Intersegment revenues 0.1 0.1 Total revenue 711.9 741.6 Net income 74.0 82.4 Regulated Natural Gas Operating revenues $ 331.5 $ 469.1 Intersegment revenues (0.1 ) 0.1 Total revenue 331.4 469.2 Net income 52.1 59.2 All Other Operating revenues (a) $ 13.4 $ 12.4 Net income (loss) 2.6 (2.8 ) Consolidated Total Operating revenues (a) $ 1,056.7 $ 1,223.2 Reconciling eliminations — (0.2 ) Total revenue $ 1,056.7 $ 1,223.0 Net income 128.7 138.8 (a) Operating revenues include $1.1 million of other affiliate revenue for the three months ended March 31, 2020 and 2019 .

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 337.4 $ 324.9 Less allowance for bad debts (22.5 ) (21.0 ) Accounts receivable, net $ 314.9 $ 303.9
Inventories	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 62.5 $ 62.6 Fuel 64.4 77.1 Natural gas 26.6 52.3 Total inventories $ 153.5 $ 192.0
Property, plant and equipment, net	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 14,449.3 $ 14,361.9 Natural gas plant 4,703.8 4,631.4 Common and other property 1,132.4 1,113.5 Plant to be retired (a) 216.5 259.9 Construction work in progress 1,061.7 912.7 Total property, plant and equipment 21,563.7 21,279.4 Less accumulated depreciation (4,934.1 ) (5,124.4 ) Property, plant and equipment, net $ 16,629.6 $ 16,155.0 (a) In 2018, the CPUC approved early retirement of PSCo’s Comanche Units 1 and 2 in approximately 2022 and 2025, respectively. PSCo also expects Craig Unit 1 to be retired early in 2025. Amounts are presented net of accumulated depreciation.

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	At March 31, 2020 , PSCo had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 700 $ 8 $ 692 (a) This credit facility expires in June 2024 . (b) Includes outstanding commercial paper and letters of credit.
Money Pool
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Money pool borrowings for PSCo were as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end 196 39 Average amount outstanding 34 7 Maximum amount outstanding 208 50 Weighted average interest rate, computed on a daily basis 1.38 % 2.29 % Weighted average interest rate at period end 1.15 1.63 %
Commercial Paper
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Commercial paper outstanding for PSCo was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 700 $ 700 Amount outstanding at period end — — Average amount outstanding 90 154 Maximum amount outstanding 230 432 Weighted average interest rate, computed on a daily basis 1.95 % 2.67 % Weighted average interest rate at period end N/A N/A

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	PSCo’s operating revenues consists of the following: Three Months Ended March 31, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 237.5 $ 217.4 $ 3.1 $ 458.0 C&I 352.0 77.8 9.2 439.0 Other 12.2 — — 12.2 Total retail 601.7 295.2 12.3 909.2 Wholesale 47.3 — — 47.3 Transmission 13.4 — — 13.4 Other 14.8 29.8 — 44.6 Total revenue from contracts with customers 677.2 325.0 12.3 1,014.5 Alternative revenue and other 34.6 6.5 1.1 42.2 Total revenues $ 711.8 $ 331.5 $ 13.4 $ 1,056.7 Three Months Ended March 31, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 245.1 $ 311.4 $ 2.5 $ 559.0 C&I 367.9 120.3 8.8 497.0 Other 12.5 — — 12.5 Total retail 625.5 431.7 11.3 1,068.5 Wholesale 57.3 — — 57.3 Transmission 13.4 — — 13.4 Other 11.6 31.6 — 43.2 Total revenue from contracts with customers 707.8 463.3 11.3 1,182.4 Alternative revenue and other 33.7 5.8 1.1 40.6 Total revenues $ 741.5 $ 469.1 $ 12.4 $ 1,223.0

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Interest Payable related to Unrecognized Tax Benefits [Table Text Block]	Interest payable related to unrecognized tax benefits: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Payable for interest related to unrecognized tax benefits at beginning of period $ (1.1 ) $ (0.7 ) Interest expense related to unrecognized tax benefits (0.1 ) (0.4 ) Payable for interest related to unrecognized tax benefits at end of period $ (1.2 ) $ (1.1 )
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following table reconciles the difference between the statutory rate and the ETR: Three Months Ended March 31 2020 2019 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 3.7 3.7 (Decreases) increases in tax from: Wind PTCs (8.0 ) (7.5 ) Plant regulatory differences (a) (4.8 ) (3.9 ) Other tax credits, net of NOL & tax credit allowances (0.1 ) (1.2 ) Other (net) 0.1 — Effective income tax rate 11.9 % 12.1 % (a) Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions.
Summary of Statute of Limitations Applicable to Open Tax Years [Table Text Block]	Federal Audits — PSCO is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows: Tax Years Expiration 2009 - 2013 September 2020 2014 - 2016 June 2021
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 7.8 $ 7.4 Unrecognized tax benefit — Temporary tax positions 4.6 4.6 Total unrecognized tax benefit $ 12.4 $ 12.0
Tax Benefits Associated with NOL and Tax Credit Carryforwards	Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (8.7 ) $ (8.3 )

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Gross Notional Amounts of Commodity Forwards and Options	Gross notional amounts of commodity forwards and options: (Amounts in Millions) (a)(b) March 31, 2020 Dec. 31, 2019 MWh of electricity 9.4 9.3 MMBtu of natural gas 50.4 32.2 (a) Amounts are not reflective of net positions in the underlying commodities. (b) Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income	Pre-Tax (Gains) Losses Pre-Tax Gains (Losses) Recognized (Millions of Dollars) Accumulated Regulatory Assets and Three Months Ended March 31, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total 0.4 — — Other derivative instruments Commodity trading — — 0.9 (b) Natural gas commodity — (1.3 ) (c) (2.0 ) (c) Total $ — $ (1.3 ) $ (1.1 ) (a) Amounts are recorded to interest charges. (b) Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate. (c) Amounts for the three months ended March 31, 2019 , included no settlement gain or losses on derivatives entered to mitigate natural gas price risk for electric generation recorded to electric fuel and purchased power, subject to cost-recovery mechanisms and reclassified to a regulatory asset, as appropriate. Remaining derivative settlement losses for the three months ended March 31, 2019 , relate to natural gas operations and are recorded to cost of natural gas sold and transported. These gains and losses are subject to cost-recovery mechanisms and reclassified out of income to a regulatory asset or liability, as appropriate. Pre-Tax Losses Pre-Tax Losses Recognized (Millions of Dollars) Accumulated Regulatory Three Months Ended March 31, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total 0.4 — — Other derivative instruments Commodity trading — — (2.1 ) (b) Natural gas commodity — 3.4 (c) (3.4 ) (c) Total $ — $ 3.4 $ (5.5 ) (a) Amounts are recorded to interest charges. (b) Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate. (c) Amounts for the three months ended March 31, 2020 , included no settlement gain or losses on derivatives entered to mitigate natural gas price risk for electric generation recorded to electric fuel and purchased power, subject to cost-recovery mechanisms and reclassified to a regulatory asset, as appropriate. Remaining derivative settlement losses for the three months ended March 31, 2020 Pre-Tax Fair Value Gains Recognized During the Period in: (Millions of Dollars) Accumulated Other Regulatory (Assets) and Liabilities Three Months Ended March 31, 2019 Other derivative instruments Natural gas commodity $ — $ 3.3 Total $ — $ 3.3
Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level	March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative assets Other derivative instruments: Commodity trading $ 4.7 $ 14.8 $ 0.6 $ 20.1 $ (15.1 ) $ 5.0 $ 1.9 $ 11.1 $ 0.9 $ 13.9 $ (10.1 ) $ 3.8 Natural gas commodity — — — — — — — 3.4 — 3.4 — 3.4 Total current derivative assets $ 4.7 $ 14.8 $ 0.6 $ 20.1 $ (15.1 ) $ 5.0 $ 1.9 $ 14.5 $ 0.9 $ 17.3 $ (10.1 ) $ 7.2 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 0.3 $ 6.8 $ 0.4 $ 7.5 $ (7.5 ) $ — $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6 ) $ — Total noncurrent derivative assets $ 0.3 $ 6.8 $ 0.4 $ 7.5 $ (7.5 ) $ — $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6 ) $ — March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative liabilities Other derivative instruments: Commodity trading $ 4.1 $ 20.2 $ — $ 24.3 $ (15.6 ) $ 8.7 $ 1.7 $ 16.7 $ — $ 18.4 $ (13.1 ) $ 5.3 Natural gas commodity — — — — — — — 3.4 — 3.4 — 3.4 Total current derivative liabilities $ 4.1 $ 20.2 $ — $ 24.3 $ (15.6 ) $ 8.7 $ 1.7 $ 20.1 $ — $ 21.8 $ (13.1 ) $ 8.7 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 0.3 $ 44.9 $ 15.6 $ 60.8 $ (12.6 ) $ 48.2 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6 ) $ 52.5 Total noncurrent derivative liabilities $ 0.3 $ 44.9 $ 15.6 $ 60.8 $ (12.6 ) $ 48.2 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6 ) $ 52.5 (a) PSCo nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at March 31, 2020 and Dec. 31, 2019 . At both March 31, 2020 and Dec. 31, 2019 , derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $5.6 million and $3.0 million , respectively. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.
Carrying Amount and Fair Value of Long-term Debt	Other financial instruments for which the carrying amount did not equal fair value: March 31, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 5,385.7 $ 5,891.1 $ 5,384.7 $ 6,039.3

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost (Credit)	Components of Net Periodic Benefit Cost (Credit) Three Months Ended March 31 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 7.6 $ 6.4 $ 0.1 $ 0.1 Interest cost (a) 11.4 12.9 3.2 3.9 Expected return on plan assets (a) (17.6 ) (17.1 ) (4.4 ) (4.7 ) Amortization of prior service credit (a) (0.7 ) (0.8 ) (1.0 ) (1.4 ) Amortization of net loss (a) 7.5 6.3 0.4 0.7 Net periodic benefit cost (credit) 8.2 7.7 (1.7 ) (1.4 ) Credits not recognized due to effects of regulation 0.6 1.9 0.6 0.3 Net benefit cost (credit) recognized for financial reporting $ 8.8 $ 9.6 $ (1.1 ) $ (1.1 ) (a) The components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Changes in Accumulated Other Comprehensive Loss, Net of Tax	Three Months Ended March 31, 2019 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (25.3 ) $ (0.2 ) $ (25.5 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 Accumulated other comprehensive loss at March 31 $ (25.0 ) $ (0.2 ) $ (25.2 ) (a) Included in interest charges. Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2020 and 2019 : Three Months Ended March 31, 2020 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (24.1 ) $ (2.5 ) $ (26.6 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 Accumulated other comprehensive loss at March 31 $ (23.8 ) $ (2.5 ) $ (26.3 ) (a) Included in interest charges.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Results from Operations by Reportable Segment	PSCo’s segment information for the three months ended March 31 : (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 711.8 $ 741.5 Intersegment revenues 0.1 0.1 Total revenue 711.9 741.6 Net income 74.0 82.4 Regulated Natural Gas Operating revenues $ 331.5 $ 469.1 Intersegment revenues (0.1 ) 0.1 Total revenue 331.4 469.2 Net income 52.1 59.2 All Other Operating revenues (a) $ 13.4 $ 12.4 Net income (loss) 2.6 (2.8 ) Consolidated Total Operating revenues (a) $ 1,056.7 $ 1,223.2 Reconciling eliminations — (0.2 ) Total revenue $ 1,056.7 $ 1,223.0 Net income 128.7 138.8 (a) Operating revenues include $1.1 million of other affiliate revenue for the three months ended March 31, 2020 and 2019 .

Selected Balance Sheet Data (De

Selected Balance Sheet Data (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts receivable, net
Accounts receivable	$ 337.4	$ 324.9
Less allowance for bad debts	(22.5)	(21)
Accounts receivable, net	$ 314.9	$ 303.9

Selected Balance Sheet Data Bal

Selected Balance Sheet Data Balance Sheet Related Disclosures, Inventories (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Public Utilities, Inventory [Line Items]
Total Inventories	$ 153.5	$ 192
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	62.5	62.6
Fuel
Public Utilities, Inventory [Line Items]
Inventories	64.4	77.1
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 26.6	$ 52.3

Selected Balance Sheet Data B_2

Selected Balance Sheet Data Balance Sheet Related Disclosures, Property, Plant and Equipment (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 21,563.7	$ 21,279.4
Less accumulated depreciation		(4,934.1)	(5,124.4)
Property, plant and equipment, net		16,629.6	16,155
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		14,449.3	14,361.9
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		4,703.8	4,631.4
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		1,132.4	1,113.5
Plant to be retired
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	[1]	216.5	259.9
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 1,061.7	$ 912.7
[1]	n 2018, the CPUC approved early retirement of PSCo’s Comanche Units 1 and 2 in approximately 2022 and 2025, respectively. PSCo also expects Craig Unit 1 to be retired early in 2025. Amounts are presented net of accumulated depreciation.

Accounting Pronouncements (Deta

Accounting Pronouncements (Details) - USD ($) $ in Millions	Jan. 01, 2020	Mar. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit Losses, Topic 326 (ASC Topic 326)		$ 0.7
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit Losses, Topic 326 (ASC Topic 326)	$ 0.7	$ 0.7

Money Pool (Details)

Money Pool (Details) - Money Pool - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Borrowing limit	$ 250,000,000	$ 250,000,000
Amount outstanding at period end	196,000,000	39,000,000
Average amount outstanding	34,000,000	7,000,000
Maximum amount outstanding	$ 208,000,000	$ 50,000,000
Weighted average interest rate, computed on a daily basis	1.38%	2.29%
Weighted average interest rate at period end	1.15%	1.63%

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments Commercial Paper (Details) - Commercial Paper - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Borrowing limit	$ 700,000,000	$ 700,000,000
Amount outstanding at period end	0	0
Average amount outstanding	90,000,000	154,000,000
Maximum amount outstanding	$ 230,000,000	$ 432,000,000
Weighted average interest rate, computed on a daily basis	1.95%	2.67%

Letters of Credit (Details)

Letters of Credit (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 8	$ 9
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Letters of Credit, Term	1 year

Credit Agreement (Details)

Credit Agreement (Details) - Credit Facility		3 Months Ended
		Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Line of Credit Facility [Line Items]
Number of extension you can request		2
Credit Facility	[1]	$ 700,000,000
Outstanding	[2]	8,000,000
Available		692,000,000
Direct advances on the credit facility outstanding		$ 0	$ 0
[1]	This credit facility expires in June 2024 .
[2]	Includes outstanding commercial paper and letters of credit.

Revenues (Details)

Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,056.7	$ 1,223
Regulated Electric
Disaggregation of Revenue [Line Items]
Total revenues	711.8	741.5
Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Total revenues	331.5	469.1
All Other
Disaggregation of Revenue [Line Items]
Total revenues	13.4	12.4
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,014.5	1,182.4
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	677.2	707.8
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	325	463.3
Total revenue from contracts with customers | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12.3	11.3
Retail
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	909.2	1,068.5
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	458	559
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	439	497
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12.2	12.5
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	601.7	625.5
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	237.5	245.1
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	352	367.9
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12.2	12.5
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	295.2	431.7
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	217.4	311.4
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	77.8	120.3
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Retail | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12.3	11.3
Retail | All Other | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.1	2.5
Retail | All Other | C&I
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	9.2	8.8
Retail | All Other | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	47.3	57.3
Wholesale | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	47.3	57.3
Wholesale | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Wholesale | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Transmission
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	13.4	13.4
Transmission | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	13.4	13.4
Transmission | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Transmission | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	44.6	43.2
Other | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	14.8	11.6
Other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	29.8	31.6
Other | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Alternative and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	42.2	40.6
Alternative and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	34.6	33.7
Alternative and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	6.5	5.8
Alternative and other | All Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 1.1	$ 1.1

Income Taxes (Details)

Income Taxes (Details)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory rate		21.00%	21.00%
State tax (net of federal tax effect)		3.70%	3.70%
Wind PTCs		(8.00%)	(7.50%)
Plant regulatory differences	[1]	(4.80%)	(3.90%)
Other tax credits and tax credit and NOL allowances (net)		(0.10%)	(1.20%)
Other (net)		0.10%	0.00%
Effective income tax rate		11.90%	12.10%
[1]	Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions.

Income Taxes Federal Audits (De

Income Taxes Federal Audits (Details)	3 Months Ended
	Mar. 31, 2020USD ($)
Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Potential Tax Adjustments	$ 0

Income Taxes Unrecognized Tax B

Income Taxes Unrecognized Tax Benefits (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefit — Permanent tax positions	$ 7,800,000	$ 7,400,000
Unrecognized tax benefit — Temporary tax positions	4,600,000	4,600,000
Total unrecognized tax benefit	12,400,000	12,000,000
NOL and tax credit carryforwards	8,700,000	8,300,000
Net Deferred Tax Liability associated with the Unrecognized Tax Benefit Amounts and Related NOLs and Tax Credit Carryforwards	(5,400,000)	(5,000,000)
Decrease in Unrecognized Tax Benefits is Reasonably Possible	8,700,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	(1,200,000)	(1,100,000)	$ (700,000)
Interest Expense (Income) related to unrecognized tax benefits	(100,000)	(400,000)
Unrecognized Tax Benefits, Income Tax Penalties Accrued	$ 0	$ 0

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities Interest Rate Derivatives (Details) $ in Millions	Mar. 31, 2020USD ($)
Interest Rate Swap [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 1.2

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Mar. 31, 2020USD ($)MMBTUMWh	Dec. 31, 2019MMBTUMWh
Cash flow hedge commodity [Member]
Derivative [Line Items]
Commodity contracts designated as cash flow hedges | $		$ 0
Electric Commodity [Member]
Gross Notional Amounts of Commodity Forwards and Options [Abstract]
Derivative, Nonmonetary Notional amount | MWh	[1],[2]	9.4	9.3
Natural Gas Commodity [Member]
Gross Notional Amounts of Commodity Forwards and Options [Abstract]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	50.4	32.2
[1]	Amounts are not reflective of net positions in the underlying commodities.
[2]	Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities Consideration of Credit Risk and Concentrations (Details)	3 Months Ended
	Mar. 31, 2020USD ($)Counterparty		Mar. 31, 2019USD ($)		Dec. 31, 2019USD ($)
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Derivative instruments designated as fair value hedges	$ 0				$ 0
Not Designated as Hedging Instrument [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in accumulated other comprehensive loss			$ 0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities			3,300,000
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	0		0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	(3,400,000)		(1,300,000)
Pre-tax gains (losses) recognized during the period in income	(5,500,000)		(1,100,000)
Not Designated as Hedging Instrument [Member] | Commodity Trading Contract [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	0		0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0
Pre-tax gains (losses) recognized during the period in income	(2,100,000)	[1]	900,000	[2]
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity Contract [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in accumulated other comprehensive loss			0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities	0		3,300,000
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	0		0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	(3,400,000)	[3]	(1,300,000)	[4]
Pre-tax gains (losses) recognized during the period in income	(3,400,000)	[3]	(2,000,000)	[4]
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity for Electric Generation [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities			0
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	400,000		400,000
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0
Pre-tax gains (losses) recognized during the period in income	0		0
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	400,000	[5]	400,000	[6]
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0
Pre-tax gains (losses) recognized during the period in income	$ 0		$ 0
Credit Concentration Risk [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty	10
Credit Concentration Risk [Member] | Municipal or Cooperative Entities or Other Utilities [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty	8
Credit Concentration Risk [Member] | External Credit Rating, Investment Grade [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty	4
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties	$ 113,300,000
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties	77.00%
Credit Concentration Risk [Member] | Internal Investment Grade [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty	5
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties	$ 20,600,000
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties	14.00%
Credit Concentration Risk [Member] | External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty	1
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties	$ 2,300,000
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties	1.00%
[1]	Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate.
[2]	Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate.
[3]	Amounts for the three months ended March 31, 2020 , included no settlement gain or losses on derivatives entered to mitigate natural gas price risk for electric generation recorded to electric fuel and purchased power, subject to cost-recovery mechanisms and reclassified to a regulatory asset, as appropriate. Remaining derivative settlement losses for the three months ended March 31, 2020
[4]	Amounts for the three months ended March 31, 2019 , included no settlement gain or losses on derivatives entered to mitigate natural gas price risk for electric generation recorded to electric fuel and purchased power, subject to cost-recovery mechanisms and reclassified to a regulatory asset, as appropriate. Remaining derivative settlement losses for the three months ended March 31, 2019
[5]	Amounts are recorded to interest charges.
[6]	Amounts are recorded to interest charges.

Credit Related Contingent Featu

Credit Related Contingent Features (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Derivative instruments in a gross liability position	$ 0	$ 0
Collateral posted related to adequate assurance clauses in derivative contracts	$ 0	$ 0

Recurring Fair Value Measures (

Recurring Fair Value Measures (Details) - USD ($)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Obligation to Return Cash		$ 0		$ 0
Right to Reclaim Cash		5,600,000		3,000,000
Commodity Trading
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings		1,000,000	$ 700,000
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers into Level 3		0
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		20,100,000		17,300,000
Netting	[1]	(15,100,000)		(10,100,000)
Derivative Asset		5,000,000		7,200,000
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		4,700,000		1,900,000
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		14,800,000		14,500,000
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		600,000		900,000
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		7,500,000		9,600,000
Netting	[1]	(7,500,000)		(9,600,000)
Derivative Asset		0		0
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		300,000		400,000
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		6,800,000		8,100,000
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		400,000		1,100,000
Fair Value Measured on a Recurring Basis | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		24,300,000		21,800,000
Netting	[1]	(15,600,000)		(13,100,000)
Derivative Liability		8,700,000		8,700,000
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		4,100,000		1,700,000
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		20,200,000		20,100,000
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0		0
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		60,800,000		62,100,000
Netting	[1]	(12,600,000)		(9,600,000)
Derivative Liability		48,200,000		52,500,000
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		300,000		400,000
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		44,900,000		47,000,000
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		15,600,000		14,700,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		20,100,000		13,900,000
Netting	[1]	(15,100,000)		(10,100,000)
Derivative Asset		5,000,000		3,800,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Commodity Trading | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		4,700,000		1,900,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Commodity Trading | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		14,800,000		11,100,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Commodity Trading | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		600,000		900,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0		3,400,000
Netting	[1]	0		0
Derivative Asset		0		3,400,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Natural Gas Commodity | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Natural Gas Commodity | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0		3,400,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Assets | Natural Gas Commodity | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Assets | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		7,500,000		9,600,000
Netting	[1]	(7,500,000)		(9,600,000)
Derivative Asset		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Assets | Commodity Trading | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		300,000		400,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Assets | Commodity Trading | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		6,800,000		8,100,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Assets | Commodity Trading | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		400,000		1,100,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		24,300,000		18,400,000
Netting	[1]	(15,600,000)		(13,100,000)
Derivative Liability		8,700,000		5,300,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Commodity Trading | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		4,100,000		1,700,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Commodity Trading | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		20,200,000		16,700,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Commodity Trading | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0		3,400,000
Netting	[1]	0		0
Derivative Liability		0		3,400,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Natural Gas Commodity | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Natural Gas Commodity | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0		3,400,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Current Liabilities | Natural Gas Commodity | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Liabilities | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		60,800,000		62,100,000
Netting	[1]	(12,600,000)		(9,600,000)
Derivative Liability		48,200,000		52,500,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Liabilities | Commodity Trading | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		300,000		400,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Liabilities | Commodity Trading | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		44,900,000		47,000,000
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Other Noncurrent Liabilities | Commodity Trading | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		$ 15,600,000		$ 14,700,000
[1]	PSCo nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at March 31, 2020 and Dec. 31, 2019 . At both March 31, 2020 and Dec. 31, 2019 , derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $5.6 million and $3.0 million , respectively. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.

Fair Value of Long-Term Debt (D

Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term Debt, Carrying Amount	$ 5,385.7	$ 5,384.7
Level 2
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, fair value	$ 5,891.1	$ 6,039.3

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended
		Jan. 31, 2020USD ($)Plan	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			$ 7.6	$ 6.4
Interest cost	[1]		11.4	12.9
Expected return on plan assets	[1]		(17.6)	(17.1)
Amortization of prior service credit	[1]		(0.7)	(0.8)
Amortization of net loss	[1]		7.5	6.3
Net periodic benefit cost (credit)			8.2	7.7
Credits (costs) not recognized due to the effects of regulation			0.6	1.9
Net benefit cost (credit) recognized for financial reporting			8.8	9.6
Contributions to pension plans		$ 50
Pension Plan [Member] | Xcel Energy Inc.
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Contributions to pension plans		$ 150
Number of Xcel Energy's pension plans to which contributions were made | Plan		4
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0.1	0.1
Interest cost	[1]		3.2	3.9
Expected return on plan assets	[1]		(4.4)	(4.7)
Amortization of prior service credit	[1]		(1)	(1.4)
Amortization of net loss	[1]		0.4	0.7
Net periodic benefit cost (credit)			(1.7)	(1.4)
Credits (costs) not recognized due to the effects of regulation			0.6	0.3
Net benefit cost (credit) recognized for financial reporting			$ (1.1)	$ (1.1)
[1]	The components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Gas Trading Litigation (Details

Gas Trading Litigation (Details)	Mar. 31, 2020
Gas Trading Litigation [Member]
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number	2

MGP, Landfill and Disposal Site

MGP, Landfill and Disposal Sites (Details)	Mar. 31, 2020
Other MGP, Landfill, or Disposal Sites [Domain]
Site Contingency [Line Items]
Number of identified MGP, landfill, or disposal sites under current investigation and/or remediation	2

Commitments and Contingencies E

Commitments and Contingencies Environmental Requirements - Water and Waste (Details) - Federal Coal Ash Regulation [Domain]	Mar. 31, 2020
Site Contingency [Line Items]
Number of sites where regulated ash units will still be in operation at a specified date	6
Number of sites where statistically significant increases over established groundwater standards exist	4
Number of sites where corrective action options are being evaluated for locations with statistically significant increases above background concentrations	2
Number of impoundments where closure plans will be expedited	1

Variable Interest Entities (Det

Variable Interest Entities (Details) - MW	Mar. 31, 2020	Dec. 31, 2019
Independent Power Producing Entities
Purchased Power Agreements [Abstract]
Generating capacity under long term purchased power agreements (in MW)	1,442	1,442

Other Comprehensive Income (Det

Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	$ 6,996.2
Accumulated other comprehensive loss at end of period	7,072
Interest rate derivatives, tax	17.4		$ 19.1
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(24.1)		(25.3)
Net current period other comprehensive loss	0.3		0.3
Accumulated other comprehensive loss at end of period	(23.8)		(25)
Gains and Losses on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss), tax	0		0
Interest rate derivatives, tax	0.1		0.1
Amortization of net actuarial loss, tax	0		0
Gains and Losses on Cash Flow Hedges | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	(0.3)	[1]	(0.3)	[2]
Defined Benefit and Postretirement Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(2.5)		(0.2)
Net current period other comprehensive loss	0		0
Accumulated other comprehensive loss at end of period	(2.5)		(0.2)
Defined Benefit and Postretirement Items | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss), tax	0		0
Interest rate derivatives, tax	0		0
Amortization of net actuarial loss, tax	0		0
Defined Benefit and Postretirement Items | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	0	[1]	0	[2]
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(26.6)		(25.5)
Net current period other comprehensive loss	0.3		0.3
Accumulated other comprehensive loss at end of period	(26.3)		(25.2)
Total | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	$ (0.3)	[1]	$ (0.3)	[2]
[1]	Included in interest charges.
[2]	Included in interest charges. Three Months Ended March 31, 2019 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (25.3 ) $ (0.2 ) $ (25.5 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 Accumulated other comprehensive loss at March 31 $ (25.0 ) $ (0.2 ) $ (25.2 ) (a) Included in interest charges.

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Net income		$ 128.7	$ 138.8
Gas		331.5	469.1
Unregulated Operating Revenue		13.4	12.4
Regulated and Unregulated Operating Revenue		1,056.7	1,223
Affiliate Revenue		1.1	1.1
Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Revenues Including Intersegment Revenues		711.9	741.6
Net income		74	82.4
Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Revenues Including Intersegment Revenues		331.4	469.2
Net income		52.1	59.2
All Other
Segment Reporting Information [Line Items]
Net income		2.6	(2.8)
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	[1]	1,056.7	1,223.2
Total revenues | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric		711.8	741.5
Total revenues | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Gas		331.5	469.1
Total revenues | All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue	[1]	13.4	12.4
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue		0	(0.2)
Intersegment Eliminations | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric		0.1	0.1
Intersegment Eliminations | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Gas		$ (0.1)	$ 0.1
[1]	Operating revenues include $1.1 million of other affiliate revenue for the three months ended March 31, 2020 and 2019 .