Public Service Co Of Colorado 10-Q 31 Jul 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Entity Central Index Key	0000081018
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity Registrant Name	Public Service Company of Colorado
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

Management's Opinion

Management's Opinion	6 Months Ended
	Jun. 30, 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 June 30, 2020 and Dec. 31, 2019; the results of its operations, including the components of net income, comprehensive income and changes in stockholder’s equity for the three and six months ended June 30, 2020 and 2019; and its cash flows for the six months ended June 30, 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 June 30, 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.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 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	6 Months Ended
	Jun. 30, 2020
Accounting Standards Update and Change in Accounting Principle [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.

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Millions	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	$ 6,298.2	$ 0	$ 4,340.5	$ 1,983.2	$ (25.5)
Increase (Decrease) in Stockholder's Equity
Net income	240.3			240.3
Other comprehensive income	0.6				0.6
Common dividends declared to parent	(203.8)			(203.8)
Contribution of capital by parent	277.8		277.8
Balance (in shares) at Jun. 30, 2019		100
Ending Balance at Jun. 30, 2019	6,613.1	$ 0	4,618.3	2,019.7	(24.9)
Balance (in shares) at Mar. 31, 2019		100
Beginning Balance at Mar. 31, 2019	6,388.4	$ 0	4,390.5	2,023.1	(25.2)
Increase (Decrease) in Stockholder's Equity
Net income	101.5			101.5
Other comprehensive income	0.3				0.3
Common dividends declared to parent	(104.9)			(104.9)
Contribution of capital by parent	227.8		227.8
Balance (in shares) at Jun. 30, 2019		100
Ending Balance at Jun. 30, 2019	$ 6,613.1	$ 0	4,618.3	2,019.7	(24.9)
Balance (in shares) at Dec. 31, 2019	100	100
Beginning Balance at Dec. 31, 2019	$ 6,996.2	$ 0	4,939.4	2,083.4	(26.6)
Increase (Decrease) in Stockholder's Equity
Net income	236.8			236.8
Other comprehensive income	0.6				0.6
Common dividends declared to parent	(567.1)			(567.1)
Contribution of capital by parent	754.3		754.3
Credit Losses, Topic 326 (ASC Topic 326)	$ (0.7)			(0.7)
Balance (in shares) at Jun. 30, 2020	100	100
Ending Balance at Jun. 30, 2020	$ 7,420.1	$ 0	5,693.7	1,752.4	(26)
Balance (in shares) at Mar. 31, 2020		100
Beginning Balance at Mar. 31, 2020	7,072	$ 0	4,989.4	2,108.9	(26.3)
Increase (Decrease) in Stockholder's Equity
Net income	108.1			108.1
Other comprehensive income	0.3				0.3
Common dividends declared to parent	(464.6)			(464.6)
Contribution of capital by parent	$ 704.3		704.3
Balance (in shares) at Jun. 30, 2020	100	100
Ending Balance at Jun. 30, 2020	$ 7,420.1	$ 0	$ 5,693.7	$ 1,752.4	$ (26)

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues
Electric	$ 715.4	$ 692.7	$ 1,427.2	$ 1,434.2
Natural gas	186.2	207.6	517.7	676.7
Steam and other	9.5	9.7	22.9	22.1
Total operating revenue	911.1	910	1,967.8	2,133
Operating expenses
Electric Fuel and Purchased Power	258.4	240.7	529.2	544.9
Cost of natural Gas Sold and Transported	49.8	69.9	187.4	342.4
Cost of sales — steam and other	3	3.9	6	8.4
Operating and maintenance expenses	189.3	200.3	393.8	399.5
Demand side management expenses	36.1	32.2	71.7	64.4
Depreciation and amortization	158.1	148.1	314.5	295
Taxes (other than income taxes)	55.4	52.2	108.6	105.9
Total operating expenses	750.1	747.3	1,611.2	1,760.5
Operating income	161	162.7	356.6	372.5
Other income (expense), net	1.6	(0.3)	(0.2)	0.6
Allowance for funds used during construction — equity	11.4	5	20	9.1
Interest charges and financing costs
Interest charges — includes other financing costs of $1.8, $1.6, $3.5 and $3.2, respectively	62.9	57.7	123	117.1
Allowance for funds used during construction — debt	(4.7)	(2.4)	(8.5)	(4.9)
Total interest charges and financing costs	58.2	55.3	114.5	112.2
Income before income taxes	115.8	112.1	261.9	270
Income tax expense	7.7	10.6	25.1	29.7
Net income	$ 108.1	$ 101.5	$ 236.8	$ 240.3

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Financial Position [Abstract]
Debt Related Commitment Fees and Debt Issuance Costs	$ 1.8	$ 1.6	$ 3.5	$ 3.2

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Comprehensive income:
Net income	$ 108.1	$ 101.5	$ 236.8	$ 240.3
Derivative instruments:
Reclassification of loss to net income, net of tax of $0.1, $0.1, $0.2, and $0.2, respectively	0.3	0.3	0.6	0.6
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0.1	0.1	0.2	0.2
Total other comprehensive income	0.3	0.3	0.6	0.6
Total comprehensive income	$ 108.4	$ 101.8	$ 237.4	$ 240.9

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net income	$ 236.8	$ 240.3
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	316.7	297.4
Deferred income taxes	8.7	2.8
Amortization of investment tax credits	(1.2)	(1.3)
Allowance for equity funds used during construction	(20)	(9.1)
Provision for Bad Debts	10.8	6.8
Net realized and unrealized hedging and derivative transactions	(1.4)	(2.2)
Changes in operating assets and liabilities:
Accounts receivable	24.5	56.4
Increase (Decrease) in Accrued Unbilled Revenues	65.3	77.2
Inventories	20.4	16.5
Prepayments and other	6.6	0.5
Accounts payable	(83.4)	(111.8)
Net regulatory assets and liabilities	41	80
Other current liabilities	(86.1)	(94.6)
Pension and other employee benefit obligations	(46.7)	(43.5)
Other Operating Activities, Cash Flow Statement	(8)	0.5
Net cash provided by operating activities	484	515.9
Investing activities
Utility capital/construction expenditures	(917.6)	(632.5)
Investments in utility money pool arrangement	(366)	(131)
Repayments from utility money pool arrangement	366	131
Net cash used in investing activities	(917.6)	(632.5)
Financing activities
Repayments of short-term borrowings, net	0	(86)
Borrowings under utility money pool arrangement	1,311	58
Repayments under utility money pool arrangement	(1,350)	(8)
Proceeds from Issuance of Long-term Debt	735.2	391.6
Repayments of Long-term Debt	0	(400)
Capital contributions from parent	778.4	332.2
Dividends paid to parent	(574.1)	(190.4)
Other, net	(0.3)	0
Net cash provided by financing activities	900.2	97.4
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	466.6	(19.2)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	478	14.2
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(106.9)	(107.4)
Cash paid for income taxes, net	(17.5)	(28.7)
Supplemental disclosure of non-cash investing and financing transactions:
Accrued property, plant and equipment additions	113.2	113.1
Inventory transfers to plant, property and equipment	17.4	15.4
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	8.2	653.4
Allowance for equity funds used during construction	$ 20	$ 9.1

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 478,000	$ 11,400
Accounts receivable, net	284,300	303,900
Accounts receivable from affiliates	13,000	52,700
Accrued unbilled revenues	227,700	293,900
Inventory, Net	154,100	192,000
Regulatory assets	87,200	64,000
Derivative instruments	8,000	7,200
Prepayments and other	57,100	55,900
Total current assets	1,309,400	981,000
Property, plant and equipment, net	16,927,800	16,155,000
Other assets
Regulatory assets	1,045,500	1,038,100
Derivative instruments	400	0
Operating Lease, Right-of-Use Asset	541,000	574,000
Other	257,100	259,400
Total other assets	1,844,000	1,871,500
Total assets	20,081,200	19,007,500
Current liabilities
Current portion of long-term debt	400,000	400,000
Borrowings Payable Under Utility Money Pool Arrangement	0	39,000
Accounts payable	354,600	573,300
Accounts payable to affiliates	63,800	43,900
Regulatory liabilities	103,700	69,200
Taxes accrued	123,300	202,100
Accrued interest	55,800	53,400
Dividends payable to parent	104,600	111,500
Derivative instruments	13,200	8,700
Operating Lease, Liability, Current	91,800	85,800
Other	85,900	98,800
Total current liabilities	1,396,700	1,685,700
Deferred credits and other liabilities
Deferred Income Tax Liabilities, Net	1,880,100	1,850,800
Deferred investment tax credits	21,600	22,800
Regulatory liabilities	2,299,000	2,036,800
Asset retirement obligations	329,500	324,000
Derivative instruments	47,600	52,500
Contract with Customer, Liability, Noncurrent	170,600	173,600
Pension and employee benefit obligations	164,500	211,900
Operating Lease, Liability, Noncurrent	477,200	517,600
Other	152,300	150,900
Total deferred credits and other liabilities	5,542,400	5,340,900
Commitments and contingencies
Capitalization
Long-term debt	5,722,000	4,984,700
Common stock — 100 shares authorized at $0.01 par value; 100 shares outstanding at June 30, 2020 and Dec. 31, 2019, respectively	$ 0	$ 0
Common stock authorized (shares)	100	100
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock outstanding (shares)	100	100
Additional paid in capital	$ 5,693,700	$ 4,939,400
Retained earnings	1,752,400	2,083,400
Accumulated other comprehensive loss	(26,000)	(26,600)
Total common stockholder’s equity	7,420,100	6,996,200
Total liabilities and equity	$ 20,081,200	$ 19,007,500

Selected Balance Sheet Data

Selected Balance Sheet Data	6 Months Ended
	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 308.2 $ 324.9 Less allowance for bad debts (23.9) (21.0) Accounts receivable, net $ 284.3 $ 303.9 (Millions of Dollars) June 30, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 62.8 $ 62.6 Fuel 67.2 77.1 Natural gas 24.1 52.3 Total inventories $ 154.1 $ 192.0 (Millions of Dollars) June 30, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 14,601.5 $ 14,361.9 Natural gas plant 4,778.1 4,631.4 Common and other property 1,133.3 1,113.5 Plant to be retired (a) 291.5 259.9 Construction work in progress 1,251.8 912.7 Total property, plant and equipment 22,056.2 21,279.4 Less accumulated depreciation (5,128.4) (5,124.4) Property, plant and equipment, net $ 16,927.8 $ 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 Financing

Borrowings and Other Financing Instruments	6 Months Ended
	Jun. 30, 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 June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end — 39 Average amount outstanding 94 7 Maximum amount outstanding 250 50 Weighted average interest rate, computed on a daily basis 0.92 % 2.29 % Weighted average interest rate at period end N/A 1.63 % Commercial Paper — Commercial paper outstanding for PSCo was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 700 $ 700 Amount outstanding at period end — — Average amount outstanding 24 154 Maximum amount outstanding 166 432 Weighted average interest rate, computed on a daily basis 0.71 % 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 June 30, 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 June 30, 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 June 30, 2020 and Dec. 31, 2019. Long-Term Borrowings During the six months ended June 30, 2020, PSCo issued $375 million in 1.90% first mortgage bonds due Jan. 15, 2031 and $375 million of 2.70% first mortgage bonds due Jan. 15, 2051.

Revenues

Revenues	6 Months Ended
	Jun. 30, 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 June 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 243.8 $ 117.7 $ 2.8 $ 364.3 C&I 351.5 39.1 5.6 396.2 Other 11.7 — — 11.7 Total retail 607.0 156.8 8.4 772.2 Wholesale 41.5 — — 41.5 Transmission 13.8 — — 13.8 Other 14.5 23.4 — 37.9 Total revenue from contracts with customers 676.8 180.2 8.4 865.4 Alternative revenue and other 38.6 6.0 1.1 45.7 Total revenues $ 715.4 $ 186.2 $ 9.5 $ 911.1 Three Months Ended June 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 211.5 $ 130.1 $ 2.8 $ 344.4 C&I 384.4 49.4 5.7 439.5 Other 11.8 — — 11.8 Total retail 607.7 179.5 8.5 795.7 Wholesale 29.1 — — 29.1 Transmission 11.6 — — 11.6 Other 6.5 23.3 — 29.8 Total revenue from contracts with customers 654.9 202.8 8.5 866.2 Alternative revenue and other 37.8 4.8 1.2 43.8 Total revenues $ 692.7 $ 207.6 $ 9.7 $ 910.0 Six Months Ended June 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 481.3 $ 335.1 $ 5.9 $ 822.3 C&I 703.5 116.9 14.8 835.2 Other 23.9 — — 23.9 Total retail 1,208.7 452.0 20.7 1,681.4 Wholesale 88.8 — — 88.8 Transmission 27.2 — — 27.2 Other 29.3 53.2 — 82.5 Total revenue from contracts with customers 1,354.0 505.2 20.7 1,879.9 Alternative revenue and other 73.2 12.5 2.2 87.9 Total revenues $ 1,427.2 $ 517.7 $ 22.9 $ 1,967.8 Six Months Ended June 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 456.6 $ 441.5 $ 5.3 $ 903.4 C&I 752.3 169.7 14.5 936.5 Other 24.3 — — 24.3 Total retail 1,233.2 611.2 19.8 1,864.2 Wholesale 86.4 — — 86.4 Transmission 25.0 — — 25.0 Other 18.1 54.9 — 73.0 Total revenue from contracts with customers 1,362.7 666.1 19.8 2,048.6 Alternative revenue and other 71.5 10.6 2.3 84.4 Total revenues $ 1,434.2 $ 676.7 $ 22.1 $ 2,133.0

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 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: Six Months Ended June 30 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 (9.8) (9.4) Plant regulatory differences (a) (4.7) (3.4) Other tax credits, net of NOL & tax credit allowances (1.1) (1.0) Other (net) 0.5 0.1 Effective income tax rate 9.6 % 11.0 % (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 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. In April 2020, Xcel Energy and Appeals reached an agreement and no material adjustments were required. In 2018, the IRS began an audit of tax years 2014 - 2016. As of June 30, 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 June 30, 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) June 30, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 8.0 $ 7.4 Unrecognized tax benefit — Temporary tax positions 4.5 4.6 Total unrecognized tax benefit $ 12.5 $ 12.0 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) June 30, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (8.1) $ (8.3) Net deferred tax liability associated with the unrecognized tax benefit amounts and related NOLs and tax credits carryforwards were $5.7 million and $5.0 million for June 30, 2020 and Dec. 31, 2019, respectively. As the IRS audit progresses and state audits resume, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $7.6 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) June 30, 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 (0.9) (0.4) Payable for interest related to unrecognized tax benefits at end of period $ (2.0) $ (1.1) No amounts were accrued for penalties related to unrecognized tax benefits as of June 30, 2020 and Dec. 31, 2019.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	6 Months Ended
	Jun. 30, 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 net asset value. 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 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, with changes in fair value prior to settlement recorded as other comprehensive income. At June 30, 2020, accumulated other comprehensive loss related to settled interest rate derivatives included $1.2 million of net losses expected to be reclassified into earnings during the next 12 months as the hedged 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 June 30, 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) June 30, 2020 Dec. 31, 2019 Megawatt hours of electricity 19.3 9.3 Million British thermal units of natural gas 69.2 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 June 30, 2020, five of PSCo’s 10 most significant counterparties for these activities, comprising $112.3 million, or 77%, of this credit exposure, had investment grade credit ratings from S&P Global Ratings, Moody’s Investor Services or Fitch Ratings. Three of the 10 most significant counterparties, comprising $15.0 million, or 10%, 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. Two of these significant counterparties, comprising $6.7 million, or 5%, of this credit exposure, had credit quality less than investment grade, based on external and internal analysis. Seven of these significant counterparties are independent system operators, municipal or cooperative electric entities, RTO’s or other utilities. The impact of derivative activity: Pre-Tax Fair Value (Millions of Dollars) Accumulated Other Regulatory (Assets) and Liabilities Three Months Ended June 30, 2020 Other derivative instruments Natural gas commodity $ — $ (2.8) Total $ — $ (2.8) Six Months Ended June 30, 2020 Other derivative instruments Natural gas commodity $ — $ (2.8) Total $ — $ (2.8) Three Months Ended June 30, 2019 Other derivative instruments Natural gas commodity $ — $ (1.5) Total $ — $ (1.5) Six Months Ended June 30, 2019 Other derivative instruments Natural gas commodity $ — $ (1.5) Total $ — $ (1.5) Pre-Tax (Gains) Losses Pre-Tax Gains (Millions of Dollars) Accumulated Regulatory Three Months Ended June 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ (1.4) (b) Total $ — $ — $ (1.4) Six Months Ended June 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.8 (a) $ — $ — Total $ 0.8 $ — $ — Other derivative instruments Commodity trading $ — $ — $ (5.3) (b) Natural gas commodity — 3.4 (c) (3.4) (c) Total $ — $ 3.4 $ (8.7) (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 and six months ended June 30, 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 and six months ended June 30, 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 (Millions of Dollars) Accumulated Regulatory Assets and Three Months Ended June 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 3.3 (b) Total $ — $ — $ 3.3 Six months ended June 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.8 (a) $ — $ — Total $ 0.8 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 4.7 (b) Natural gas commodity — (1.3) (c) (2.0) (c) Total $ — $ (1.3) $ 2.7 (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 and six months ended June 30, 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 and six months ended June 30, 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 and six months ended June 30, 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 June 30, 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 June 30, 2020 and Dec. 31, 2019. Recurring Fair Value Measurements — PSCo’s derivative assets and liabilities measured at fair value on a recurring basis: June 30, 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 $ 2.9 $ 17.0 $ 1.0 $ 20.9 $ (18.2) $ 2.7 $ 1.9 $ 11.1 $ 0.9 $ 13.9 $ (10.1) $ 3.8 Natural gas commodity — 5.3 — 5.3 — 5.3 — 3.4 — 3.4 — 3.4 Total current derivative assets $ 2.9 $ 22.3 $ 1.0 $ 26.2 $ (18.2) $ 8.0 $ 1.9 $ 14.5 $ 0.9 $ 17.3 $ (10.1) $ 7.2 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 1.1 $ 10.8 $ — $ 11.9 $ (11.5) $ 0.4 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — Total noncurrent derivative assets $ 1.1 $ 10.8 $ — $ 11.9 $ (11.5) $ 0.4 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — June 30, 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 $ 2.5 $ 24.8 $ 0.1 $ 27.4 $ (18.2) $ 9.2 $ 1.7 $ 16.7 $ — $ 18.4 $ (13.1) $ 5.3 Natural gas commodity — 4.0 — 4.0 — 4.0 — 3.4 — 3.4 — 3.4 Total current derivative liabilities $ 2.5 $ 28.8 $ 0.1 $ 31.4 $ (18.2) $ 13.2 $ 1.7 $ 20.1 $ — $ 21.8 $ (13.1) $ 8.7 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 1.2 $ 43.1 $ 18.0 $ 62.3 $ (14.7) $ 47.6 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6) $ 52.5 Total noncurrent derivative liabilities $ 1.2 $ 43.1 $ 18.0 $ 62.3 $ (14.7) $ 47.6 $ 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 June 30, 2020 and Dec. 31, 2019. At both June 30, 2020 and Dec. 31, 2019, derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $3.2 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. Changes in Level 3 commodity derivatives: Three Months Ended June 30 (Millions of Dollars) 2020 2019 Balance at April 1 $ (14.6) $ (0.1) Settlements (0.3) — Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (2.2) 0.3 Balance at June 30 $ (17.1) $ 0.2 Six Months Ended June 30 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ (12.7) $ 0.1 Settlements (1.1) (0.9) Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (3.3) 1.0 Balance at June 30 $ (17.1) $ 0.2 (a) Amounts relate to commodity derivatives held at the end of the period. 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 and six months ended June 30, 2020 and 2019. Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: June 30, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Fair Value Carrying Fair Value Long-term debt, including current portion $ 6,122.0 $ 7,250.8 $ 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 June 30, 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	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost (Credit) Three Months Ended June 30 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) (1.3) Amortization of net loss (a) 7.5 6.3 0.4 0.7 Net periodic benefit cost (credit) 8.2 7.7 (1.7) (1.3) Credits not recognized due to effects of regulation (0.3) 1.8 1.0 0.2 Net benefit cost (credit) recognized for financial reporting $ 7.9 $ 9.5 $ (0.7) $ (1.1) Six Months Ended June 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 15.3 $ 12.8 $ 0.1 $ 0.2 Interest cost (a) 22.9 25.8 6.4 7.8 Expected return on plan assets (a) (35.3) (34.2) (8.7) (9.4) Amortization of prior service credit (a) (1.4) (1.7) (1.9) (2.7) Amortization of net loss (a) 14.9 12.7 0.8 1.5 Net periodic benefit cost (credit) 16.4 15.4 (3.3) (2.6) Credits not recognized due to effects of regulation 0.3 3.6 1.6 0.5 Net benefit cost (credit) recognized for financial reporting $ 16.7 $ 19.0 $ (1.7) $ (2.1) (a) The components of net periodic cost other than the service cost component are included in the line item “other income (expense), 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	6 Months Ended
	Jun. 30, 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. In June 2020, PSCo resolved claims by the current property owner and agreed to contribute up to a maximum of $9.3 million towards future environmental investigation, remediation and mitigation measures over the next 15 years. 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 levels above background concentrations were detected at four locations. Subsequently, assessment monitoring samples were collected at these locations and, based on the results, PSCo is evaluating options for corrective action at two locations. At one location, monitoring results indicate potential offsite impacts to groundwater. 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. In March 2020, the EPA published a proposed CCR Rule amendment that, if adopted, would allow unlined impoundments that ‘perform as effectively’ as lined ones to continue to operate under a state or federal CCR permit program. PSCo is pursuing options to provide alternative storage capacity consistent with the CCR Rule until the generating units are retired in 2025. 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 1,518 MW and 1,442 MW of capacity under long-term PPAs at June 30, 2020 and Dec. 31, 2019, respectively, 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 (Los

Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 30, 2020
Stockholders' Equity Note [Abstract]
Other Comprehensive Income	Changes in accumulated other comprehensive loss, net of tax, for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 Three Months Ended June 30, 2019 (Millions of Dollars) Gains and Losses Defined Benefit Pension and Total Gains and Losses Defined Benefit Pension and Total Accumulated other comprehensive loss at April 1 $ (23.8) $ (2.5) $ (26.3) $ (25.0) $ (0.2) $ (25.2) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1, $—, $0.1 and $—, respectively) (a) 0.3 — 0.3 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 0.3 — 0.3 Accumulated other comprehensive loss at June 30 $ (23.5) $ (2.5) $ (26.0) $ (24.7) $ (0.2) $ (24.9) (a) Included in interest charges. Six Months Ended June 30, 2020 Six Months Ended June 30, 2019 (Millions of Dollars) Gains and Losses Defined Benefit Pension and Total Gains and Losses Defined Benefit Pension and Total Accumulated other comprehensive loss at Jan. 1 $ (24.1) $ (2.5) $ (26.6) $ (25.3) $ (0.2) $ (25.5) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.2, $—, $0.1 and $—, respectively) (a) 0.6 — 0.6 0.6 — 0.6 Net current period other comprehensive income 0.6 — 0.6 0.6 — 0.6 Accumulated other comprehensive loss at June 30 $ (23.5) $ (2.5) $ (26.0) $ (24.7) $ (0.2) $ (24.9) (a) Included in interest charges.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 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 non-utility 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 and six months ended June 30: Three Months Ended June 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 715.4 $ 692.7 Intersegment revenues 0.1 0.1 Total revenue $ 715.5 $ 692.8 Net income 89.0 84.8 Regulated Natural Gas Operating revenues $ 186.2 $ 207.6 Net income 16.0 17.6 All Other Operating revenues (a) $ 9.5 $ 9.7 Net income (loss) 3.1 (0.9) Consolidated Total Operating revenues (a) $ 911.2 $ 910.1 Reconciling eliminations (0.1) (0.1) Total operating revenues $ 911.1 $ 910.0 Net income 108.1 101.5 (a) Operating revenues include $1.1 million of other affiliate revenue for the three months ended June 30, 2020 and 2019. Six Months Ended June 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 1,427.2 $ 1,434.2 Intersegment revenues 0.2 0.2 Total revenue $ 1,427.4 $ 1,434.4 Net income 163.0 167.2 Regulated Natural Gas Operating revenues $ 517.7 $ 676.7 Intersegment revenues (0.1) 0.1 Total revenue $ 517.6 $ 676.8 Net income 68.1 76.8 All Other Operating revenues (a) $ 22.9 $ 22.1 Net income (loss) 5.7 (3.7) Consolidated Total Operating revenues (a) $ 1,967.9 $ 2,133.3 Reconciling eliminations (0.1) (0.3) Total operating revenues $ 1,967.8 $ 2,133.0 Net income 236.8 240.3 (a) Operating revenues include $2.2 million of other affiliate revenue for the six months ended June 30, 2020 and 2019.

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	6 Months Ended
	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 308.2 $ 324.9 Less allowance for bad debts (23.9) (21.0) Accounts receivable, net $ 284.3 $ 303.9
Inventories	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 62.8 $ 62.6 Fuel 67.2 77.1 Natural gas 24.1 52.3 Total inventories $ 154.1 $ 192.0
Property, Plant and Equipment, Net	(Millions of Dollars) June 30, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 14,601.5 $ 14,361.9 Natural gas plant 4,778.1 4,631.4 Common and other property 1,133.3 1,113.5 Plant to be retired (a) 291.5 259.9 Construction work in progress 1,251.8 912.7 Total property, plant and equipment 22,056.2 21,279.4 Less accumulated depreciation (5,128.4) (5,124.4) Property, plant and equipment, net $ 16,927.8 $ 16,155.0

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
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 June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 700 $ 700 Amount outstanding at period end — — Average amount outstanding 24 154 Maximum amount outstanding 166 432 Weighted average interest rate, computed on a daily basis 0.71 % 2.67 % Weighted average interest rate at period end N/A N/A
Credit Facilities	At June 30, 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 June 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end — 39 Average amount outstanding 94 7 Maximum amount outstanding 250 50 Weighted average interest rate, computed on a daily basis 0.92 % 2.29 % Weighted average interest rate at period end N/A 1.63 %

Revenues (Tables)

Revenues (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	PSCo’s operating revenues consists of the following: Three Months Ended June 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 243.8 $ 117.7 $ 2.8 $ 364.3 C&I 351.5 39.1 5.6 396.2 Other 11.7 — — 11.7 Total retail 607.0 156.8 8.4 772.2 Wholesale 41.5 — — 41.5 Transmission 13.8 — — 13.8 Other 14.5 23.4 — 37.9 Total revenue from contracts with customers 676.8 180.2 8.4 865.4 Alternative revenue and other 38.6 6.0 1.1 45.7 Total revenues $ 715.4 $ 186.2 $ 9.5 $ 911.1 Three Months Ended June 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 211.5 $ 130.1 $ 2.8 $ 344.4 C&I 384.4 49.4 5.7 439.5 Other 11.8 — — 11.8 Total retail 607.7 179.5 8.5 795.7 Wholesale 29.1 — — 29.1 Transmission 11.6 — — 11.6 Other 6.5 23.3 — 29.8 Total revenue from contracts with customers 654.9 202.8 8.5 866.2 Alternative revenue and other 37.8 4.8 1.2 43.8 Total revenues $ 692.7 $ 207.6 $ 9.7 $ 910.0 Six Months Ended June 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 481.3 $ 335.1 $ 5.9 $ 822.3 C&I 703.5 116.9 14.8 835.2 Other 23.9 — — 23.9 Total retail 1,208.7 452.0 20.7 1,681.4 Wholesale 88.8 — — 88.8 Transmission 27.2 — — 27.2 Other 29.3 53.2 — 82.5 Total revenue from contracts with customers 1,354.0 505.2 20.7 1,879.9 Alternative revenue and other 73.2 12.5 2.2 87.9 Total revenues $ 1,427.2 $ 517.7 $ 22.9 $ 1,967.8 Six Months Ended June 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 456.6 $ 441.5 $ 5.3 $ 903.4 C&I 752.3 169.7 14.5 936.5 Other 24.3 — — 24.3 Total retail 1,233.2 611.2 19.8 1,864.2 Wholesale 86.4 — — 86.4 Transmission 25.0 — — 25.0 Other 18.1 54.9 — 73.0 Total revenue from contracts with customers 1,362.7 666.1 19.8 2,048.6 Alternative revenue and other 71.5 10.6 2.3 84.4 Total revenues $ 1,434.2 $ 676.7 $ 22.1 $ 2,133.0

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following table reconciles the difference between the statutory rate and the ETR: Six Months Ended June 30 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 (9.8) (9.4) Plant regulatory differences (a) (4.7) (3.4) Other tax credits, net of NOL & tax credit allowances (1.1) (1.0) Other (net) 0.5 0.1 Effective income tax rate 9.6 % 11.0 % (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) June 30, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 8.0 $ 7.4 Unrecognized tax benefit — Temporary tax positions 4.5 4.6 Total unrecognized tax benefit $ 12.5 $ 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) June 30, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (8.1) $ (8.3)
Interest Payable related to Unrecognized Tax Benefits [Table Text Block]	Interest payable related to unrecognized tax benefits: (Millions of Dollars) June 30, 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 (0.9) (0.4) Payable for interest related to unrecognized tax benefits at end of period $ (2.0) $ (1.1)

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 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) June 30, 2020 Dec. 31, 2019 Megawatt hours of electricity 19.3 9.3 Million British thermal units of natural gas 69.2 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 Fair Value (Millions of Dollars) Accumulated Other Regulatory (Assets) and Liabilities Three Months Ended June 30, 2020 Other derivative instruments Natural gas commodity $ — $ (2.8) Total $ — $ (2.8) Six Months Ended June 30, 2020 Other derivative instruments Natural gas commodity $ — $ (2.8) Total $ — $ (2.8) Three Months Ended June 30, 2019 Other derivative instruments Natural gas commodity $ — $ (1.5) Total $ — $ (1.5) Six Months Ended June 30, 2019 Other derivative instruments Natural gas commodity $ — $ (1.5) Total $ — $ (1.5) Pre-Tax (Gains) Losses Pre-Tax Gains (Millions of Dollars) Accumulated Regulatory Three Months Ended June 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ (1.4) (b) Total $ — $ — $ (1.4) Six Months Ended June 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.8 (a) $ — $ — Total $ 0.8 $ — $ — Other derivative instruments Commodity trading $ — $ — $ (5.3) (b) Natural gas commodity — 3.4 (c) (3.4) (c) Total $ — $ 3.4 $ (8.7) (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 and six months ended June 30, 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 and six months ended June 30, 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 (Millions of Dollars) Accumulated Regulatory Assets and Three Months Ended June 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 3.3 (b) Total $ — $ — $ 3.3 Six months ended June 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.8 (a) $ — $ — Total $ 0.8 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 4.7 (b) Natural gas commodity — (1.3) (c) (2.0) (c) Total $ — $ (1.3) $ 2.7 (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.
Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level	June 30, 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 $ 2.9 $ 17.0 $ 1.0 $ 20.9 $ (18.2) $ 2.7 $ 1.9 $ 11.1 $ 0.9 $ 13.9 $ (10.1) $ 3.8 Natural gas commodity — 5.3 — 5.3 — 5.3 — 3.4 — 3.4 — 3.4 Total current derivative assets $ 2.9 $ 22.3 $ 1.0 $ 26.2 $ (18.2) $ 8.0 $ 1.9 $ 14.5 $ 0.9 $ 17.3 $ (10.1) $ 7.2 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 1.1 $ 10.8 $ — $ 11.9 $ (11.5) $ 0.4 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — Total noncurrent derivative assets $ 1.1 $ 10.8 $ — $ 11.9 $ (11.5) $ 0.4 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — June 30, 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 $ 2.5 $ 24.8 $ 0.1 $ 27.4 $ (18.2) $ 9.2 $ 1.7 $ 16.7 $ — $ 18.4 $ (13.1) $ 5.3 Natural gas commodity — 4.0 — 4.0 — 4.0 — 3.4 — 3.4 — 3.4 Total current derivative liabilities $ 2.5 $ 28.8 $ 0.1 $ 31.4 $ (18.2) $ 13.2 $ 1.7 $ 20.1 $ — $ 21.8 $ (13.1) $ 8.7 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 1.2 $ 43.1 $ 18.0 $ 62.3 $ (14.7) $ 47.6 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6) $ 52.5 Total noncurrent derivative liabilities $ 1.2 $ 43.1 $ 18.0 $ 62.3 $ (14.7) $ 47.6 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6) $ 52.5
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation	Changes in Level 3 commodity derivatives: Three Months Ended June 30 (Millions of Dollars) 2020 2019 Balance at April 1 $ (14.6) $ (0.1) Settlements (0.3) — Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (2.2) 0.3 Balance at June 30 $ (17.1) $ 0.2 Six Months Ended June 30 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ (12.7) $ 0.1 Settlements (1.1) (0.9) Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (3.3) 1.0 Balance at June 30 $ (17.1) $ 0.2 (a) Amounts relate to commodity derivatives held at the end of the period.
Carrying Amount and Fair Value of Long-term Debt	Other financial instruments for which the carrying amount did not equal fair value: June 30, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Fair Value Carrying Fair Value Long-term debt, including current portion $ 6,122.0 $ 7,250.8 $ 5,384.7 $ 6,039.3

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost (Credit)	Components of Net Periodic Benefit Cost (Credit) Three Months Ended June 30 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) (1.3) Amortization of net loss (a) 7.5 6.3 0.4 0.7 Net periodic benefit cost (credit) 8.2 7.7 (1.7) (1.3) Credits not recognized due to effects of regulation (0.3) 1.8 1.0 0.2 Net benefit cost (credit) recognized for financial reporting $ 7.9 $ 9.5 $ (0.7) $ (1.1) Six Months Ended June 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 15.3 $ 12.8 $ 0.1 $ 0.2 Interest cost (a) 22.9 25.8 6.4 7.8 Expected return on plan assets (a) (35.3) (34.2) (8.7) (9.4) Amortization of prior service credit (a) (1.4) (1.7) (1.9) (2.7) Amortization of net loss (a) 14.9 12.7 0.8 1.5 Net periodic benefit cost (credit) 16.4 15.4 (3.3) (2.6) Credits not recognized due to effects of regulation 0.3 3.6 1.6 0.5 Net benefit cost (credit) recognized for financial reporting $ 16.7 $ 19.0 $ (1.7) $ (2.1) (a) The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.	[1]
[1]	The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 2020
Stockholders' Equity Note [Abstract]
Changes in Accumulated Other Comprehensive Loss, Net of Tax	Changes in accumulated other comprehensive loss, net of tax, for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 Three Months Ended June 30, 2019 (Millions of Dollars) Gains and Losses Defined Benefit Pension and Total Gains and Losses Defined Benefit Pension and Total Accumulated other comprehensive loss at April 1 $ (23.8) $ (2.5) $ (26.3) $ (25.0) $ (0.2) $ (25.2) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1, $—, $0.1 and $—, respectively) (a) 0.3 — 0.3 0.3 — 0.3 Net current period other comprehensive income 0.3 — 0.3 0.3 — 0.3 Accumulated other comprehensive loss at June 30 $ (23.5) $ (2.5) $ (26.0) $ (24.7) $ (0.2) $ (24.9)

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Results from Operations by Reportable Segment	PSCo’s segment information for the three and six months ended June 30: Three Months Ended June 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 715.4 $ 692.7 Intersegment revenues 0.1 0.1 Total revenue $ 715.5 $ 692.8 Net income 89.0 84.8 Regulated Natural Gas Operating revenues $ 186.2 $ 207.6 Net income 16.0 17.6 All Other Operating revenues (a) $ 9.5 $ 9.7 Net income (loss) 3.1 (0.9) Consolidated Total Operating revenues (a) $ 911.2 $ 910.1 Reconciling eliminations (0.1) (0.1) Total operating revenues $ 911.1 $ 910.0 Net income 108.1 101.5 (a) Operating revenues include $1.1 million of other affiliate revenue for the three months ended June 30, 2020 and 2019. Six Months Ended June 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 1,427.2 $ 1,434.2 Intersegment revenues 0.2 0.2 Total revenue $ 1,427.4 $ 1,434.4 Net income 163.0 167.2 Regulated Natural Gas Operating revenues $ 517.7 $ 676.7 Intersegment revenues (0.1) 0.1 Total revenue $ 517.6 $ 676.8 Net income 68.1 76.8 All Other Operating revenues (a) $ 22.9 $ 22.1 Net income (loss) 5.7 (3.7) Consolidated Total Operating revenues (a) $ 1,967.9 $ 2,133.3 Reconciling eliminations (0.1) (0.3) Total operating revenues $ 1,967.8 $ 2,133.0 Net income 236.8 240.3	[1],[2]
[1]	Operating revenues include $1.1 million of other affiliate revenue for the three months ended June 30, 2020 and 2019.
[2]	Operating revenues include $2.2 million of other affiliate revenue for the six months ended June 30, 2020 and 2019.

Selected Balance Sheet Data (De

Selected Balance Sheet Data (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Accounts receivable, net
Accounts receivable	$ 308.2	$ 324.9
Less allowance for bad debts	(23.9)	(21)
Accounts receivable, net	$ 284.3	$ 303.9

Selected Balance Sheet Data Bal

Selected Balance Sheet Data Balance Sheet Related Disclosures, Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Public Utilities, Inventory [Line Items]
Inventory, Net	$ 154,100	$ 192,000
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	62,800	62,600
Fuel
Public Utilities, Inventory [Line Items]
Inventories	67,200	77,100
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 24,100	$ 52,300

Selected Balance Sheet Data B_2

Selected Balance Sheet Data Balance Sheet Related Disclosures, Property, Plant and Equipment (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 22,056.2	$ 21,279.4
Less accumulated depreciation		(5,128.4)	(5,124.4)
Property, plant and equipment, net		16,927.8	16,155
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		14,601.5	14,361.9
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		4,778.1	4,631.4
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		1,133.3	1,113.5
Plant to be retired
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	[1]	291.5	259.9
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 1,251.8	$ 912.7
[1]	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.

Accounting Pronouncements (Deta

Accounting Pronouncements (Details) - USD ($) $ in Millions	Jan. 01, 2020	Jun. 30, 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

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments - Short-Term Borrowings (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Money Pool
Short-term Debt [Line Items]
Borrowing limit	$ 250,000,000	$ 250,000,000
Short-term Debt	0	39,000,000
Average amount outstanding	94,000,000	7,000,000
Maximum amount outstanding	$ 250,000,000	$ 50,000,000
Weighted average interest rate, computed on a daily basis (percentage)	0.92%	2.29%
Short-term Debt, Weighted Average Interest Rate, at Point in Time		1.63%
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	$ 700,000,000	$ 700,000,000
Short-term Debt	0	0
Average amount outstanding	24,000,000	154,000,000
Maximum amount outstanding	$ 166,000,000	$ 432,000,000
Weighted average interest rate, computed on a daily basis (percentage)	0.71%	2.67%

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments - Letters of Credit (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Term of letters of credit (in years)	1 year
Letter of Credit
Line of Credit Facility [Line Items]
Short-term Debt	$ 8	$ 9
Letter of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Term of letters of credit (in years)	1 year

Borrowings and Other Financin_5

Borrowings and Other Financing Instruments - Credit Facility (Details)		6 Months Ended
		Jun. 30, 2020USD ($)Plan	Dec. 31, 2019USD ($)
Line of Credit Facility [Line Items]
Term of letters of credit (in years)		1 year
Number of extension you can request | Plan		2
Credit Facility
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 700,000,000
Drawn	[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.

Borrowings and Other Financin_6

Borrowings and Other Financing Instruments - Borrowings and Other Financing Instruments, Long-Term Borrowings and Other Financing Instruments (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	May 15, 2020
Debt Instrument [Line Items]
Term of letters of credit (in years)	1 year
Bonds [Member] | Series Due Jan. 15, 2051 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 375,000,000
Debt Instrument, Interest Rate, Stated Percentage		2.70%
Bonds [Member] | Series due Jan. 15, 2031 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 375,000,000
Debt Instrument, Interest Rate, Stated Percentage		1.90%

Revenues (Details)

Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 865.4	$ 866.2	$ 1,879.9	$ 2,048.6
Retail
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	772.2	795.7	1,681.4	1,864.2
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	364.3	344.4	822.3	903.4
Retail | Commercial and Industrial Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	396.2	439.5	835.2	936.5
Retail | Other Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11.7	11.8	23.9	24.3
Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41.5	29.1	88.8	86.4
Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13.8	11.6	27.2	25
Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	37.9	29.8	82.5	73
Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue Not from Contract with Customer	45.7	43.8	87.9	84.4
Regulated Electric | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	676.8	654.9	1,354	1,362.7
Regulated Electric | Retail
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	607	607.7	1,208.7	1,233.2
Regulated Electric | Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	243.8	211.5	481.3	456.6
Regulated Electric | Retail | Commercial and Industrial Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	351.5	384.4	703.5	752.3
Regulated Electric | Retail | Other Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11.7	11.8	23.9	24.3
Regulated Electric | Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41.5	29.1	88.8	86.4
Regulated Electric | Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13.8	11.6	27.2	25
Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	14.5	6.5	29.3	18.1
Regulated Electric | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue Not from Contract with Customer	38.6	37.8	73.2	71.5
Regulated Natural Gas | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	180.2	202.8	505.2	666.1
Regulated Natural Gas | Retail
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	156.8	179.5	452	611.2
Regulated Natural Gas | Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	117.7	130.1	335.1	441.5
Regulated Natural Gas | Retail | Commercial and Industrial Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	39.1	49.4	116.9	169.7
Regulated Natural Gas | Retail | Other Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Regulated Natural Gas | Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Regulated Natural Gas | Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	23.4	23.3	53.2	54.9
Regulated Natural Gas | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue Not from Contract with Customer	6	4.8	12.5	10.6
All Other | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	8.4	8.5	20.7	19.8
All Other | Retail
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	8.4	8.5	20.7	19.8
All Other | Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2.8	2.8	5.9	5.3
All Other | Retail | Commercial and Industrial Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5.6	5.7	14.8	14.5
All Other | Retail | Other Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
All Other | Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
All Other | Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
All Other | Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
All Other | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue Not from Contract with Customer	1.1	1.2	2.2	2.3
Total revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	911.1	910	1,967.8	2,133
Total revenues | Regulated Electric
Disaggregation of Revenue [Line Items]
Total operating revenues	715.4	692.7	1,427.2	1,434.2
Total revenues | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Total operating revenues	186.2	207.6	517.7	676.7
Total revenues | All Other
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 9.5	$ 9.7	$ 22.9	$ 22.1

Income Taxes (Details)

Income Taxes (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 12,500,000		$ 12,000,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	3.70%	3.70%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	(9.80%)	(9.40%)
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	(4.70%)	(3.40%)
Regulatory differences - reversal of prior quarters' ARAM deferral (b)	(1.10%)	(1.00%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	0.50%	0.10%
Effective Income Tax Rate Reconciliation, Percent	9.60%	11.00%
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit — Permanent tax positions	$ 8,000,000		7,400,000
Unrecognized tax benefit — Temporary tax positions	4,500,000		4,600,000
Total unrecognized tax benefit	12,500,000		12,000,000
NOL and tax credit carryforwards	(8,100,000)		(8,300,000)
Net Deferred Tax Liability associated with the Unrecognized Tax Benefit Amounts and Related NOLs and Tax Credit Carryforwards	(5,700,000)		(5,000,000)
Upper bound of decrease in unrecognized tax benefit that is reasonably possible	7,600,000
Amounts accrued for penalties related to unrecognized tax benefits	0		0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Payable for interest related to unrecognized tax benefits at beginning of period	(1,100,000)	$ (700,000)	(700,000)
Interest expense related to unrecognized tax benefits	(900,000)		(400,000)
Payable for interest related to unrecognized tax benefits at end of period	(2,000,000)		$ (1,100,000)
Income Tax Examination [Line Items]
Income Tax Credits and Adjustments	$ 0

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Derivative Instruments (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Jun. 30, 2020USD ($)MWhMMBTUCounterparty	Dec. 31, 2019MWhMMBTU
Credit Concentration Risk
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		10
Credit Concentration Risk | Municipal or Cooperative Entities or Other Utilities [Member]
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		7
Credit Concentration Risk | External Credit Rating, Investment Grade [Member]
Consideration of Credit Risk and Concentrations [Abstract]
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 | $		$ 112.3
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)		77.00%
Credit Concentration Risk | No Investment Grade Ratings from External Credit Rating Agencies [Member]
Consideration of Credit Risk and Concentrations [Abstract]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		3
Wholesale, trading and non-trading commodity credit exposure for the most significant counterparties | $		$ 15
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)		10.00%
Interest Rate Swap
Interest Rate Derivatives [Abstract]
Amount of accumulated other comprehensive gains (losses) related to interest rate derivatives expected to be reclassified into earnings within the next twelve months | $		$ 1.2
Electric Commodity (in megawatt hours)
Gross Notional Amounts of Commodity Forwards and Options [Abstract]
Derivative, Nonmonetary Notional amount | MWh	[1],[2]	19.3	9.3
Natural Gas Commodity (in million British thermal units)
Gross Notional Amounts of Commodity Forwards and Options [Abstract]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	69.2	32.2
cash flow hedge commodity [Member]
Commodity Derivatives [Abstract]
Commodity contracts designated as cash flow hedges | $		$ 0
[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_4

Fair Value of Financial Assets and Liabilities - Impact of Derivative Activity (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019
Financial Impact of Qualifying Fair Value Hedges on Earnings [Abstract]
Derivative instruments designated as fair value hedges	$ 0		$ 0		$ 0		$ 0
Designated as Hedging Instrument | Cash Flow Hedges
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	0.4		0.4		0.8		0.8
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0		0		0
Pre-tax gains (losses) recognized during the period in income	0		0		0		0
Designated as Hedging Instrument | Cash Flow Hedges | Interest Rate
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	0.4	[1]	0.4	[2]	0.8	[1]	0.8	[2]
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0		0		0
Pre-tax gains (losses) recognized during the period in income	0		0		0		0
Other Derivative Instruments
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		0		0		0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities	(2.8)		(1.5)		(2.8)		(1.5)
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	0		0		0		0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0		3.4		1.3
Pre-tax gains (losses) recognized during the period in income	(1.4)		3.3		(8.7)		2.7
Other Derivative Instruments | Commodity Trading
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		0		0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	0		0		0		0
Pre-tax gains (losses) recognized during the period in income	(1.4)	[3]	3.3	[4]	(5.3)	[3]	4.7	[4]
Other Derivative Instruments | Natural Gas Commodity
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		0		0		0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities	(2.8)		(1.5)		(2.8)		(1.5)
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)					3.4	[5]	1.3	[6]
Pre-tax gains (losses) recognized during the period in income					(3.4)	[5]	(2)	[6]
Other Derivative Instruments | Natural Gas [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		$ 0		$ 0		$ 0
[1]	Amounts are recorded to interest charges.
[2]	Amounts are recorded to interest charges.
[3]	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.
[4]	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.
[5]	Amounts for the three and six months ended June 30, 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 and six months ended June 30, 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.
[6]	Amounts for the three and six months ended June 30, 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 and six months ended June 30, 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.

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Credit Related Contingent Features (Details) - USD ($) $ in Millions	Jun. 30, 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

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities - Derivative Assets and Liabilities at Fair Value (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset		$ 0	$ 0
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		3.2	3
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		8	7.2
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1]	(18.2)	(10.1)
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		2.7	3.8
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1]	(18.2)	(10.1)
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		5.3	3.4
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1]	0	0
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0.4	0
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1]	(11.5)	(9.6)
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0.4	0
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1]	(11.5)	(9.6)
Fair Value Measured on a Recurring Basis | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		13.2	8.7
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1]	(18.2)	(13.1)
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		9.2	5.3
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1]	(18.2)	(13.1)
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		4	3.4
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1]	0	0
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		47.6	52.5
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1]	(14.7)	(9.6)
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		47.6	52.5
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1]	(14.7)	(9.6)
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		2.9	1.9
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		2.9	1.9
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	0
Fair Value Measured on a Recurring Basis | Level 1 | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		1.1	0.4
Fair Value Measured on a Recurring Basis | Level 1 | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		1.1	0.4
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		2.5	1.7
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		2.5	1.7
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		0	0
Fair Value Measured on a Recurring Basis | Level 1 | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		1.2	0.4
Fair Value Measured on a Recurring Basis | Level 1 | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		1.2	0.4
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		22.3	14.5
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		17	11.1
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		5.3	3.4
Fair Value Measured on a Recurring Basis | Level 2 | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		10.8	8.1
Fair Value Measured on a Recurring Basis | Level 2 | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		10.8	8.1
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		28.8	20.1
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		24.8	16.7
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		4	3.4
Fair Value Measured on a Recurring Basis | Level 2 | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		43.1	47
Fair Value Measured on a Recurring Basis | Level 2 | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		43.1	47
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		1	0.9
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		1	0.9
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	0
Fair Value Measured on a Recurring Basis | Level 3 | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	1.1
Fair Value Measured on a Recurring Basis | Level 3 | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	1.1
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		0.1	0
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		0.1	0
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		0	0
Fair Value Measured on a Recurring Basis | Level 3 | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		18	14.7
Fair Value Measured on a Recurring Basis | Level 3 | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		18	14.7
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		26.2	17.3
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		20.9	13.9
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		5.3	3.4
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		11.9	9.6
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		11.9	9.6
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		31.4	21.8
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		27.4	18.4
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		62.3	62.1
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		$ 62.3	$ 62.1
[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 June 30, 2020 and Dec. 31, 2019. At both June 30, 2020 and Dec. 31, 2019, derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $3.2 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 Financial Asset_7

Fair Value of Financial Assets and Liabilities - Changes in Level 3 Commodity Derivatives (Details) - Commodity Contract - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs		$ (17.1)	$ 0.2	$ (17.1)	$ 0.2	$ (14.6)	$ (12.7)	$ (0.1)	$ 0.1
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Settlements		(0.3)	0	(1.1)	(0.9)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	[1]	(2.2)	0.3	(3.3)	1
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers, Net		$ 0	$ 0	$ 0	$ 0
[1]	Amounts relate to commodity derivatives held at the end of the period.

Fair Value of Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Carrying Amount
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, including current portion	$ 6,122	$ 5,384.7
Fair Value
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, including current portion	$ 7,250.8	$ 6,039.3

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
		Jan. 31, 2020USD ($)Plan	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			$ 7.6	$ 6.4	$ 15.3	$ 12.8
Interest cost	[1]		11.4	12.9	22.9	25.8
Expected return on plan assets	[1]		(17.6)	(17.1)	(35.3)	(34.2)
Amortization of prior service credit	[1]		(0.7)	(0.8)	(1.4)	(1.7)
Amortization of net loss	[1]		7.5	6.3	14.9	12.7
Net periodic benefit cost (credit)			8.2	7.7	16.4	15.4
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation			(0.3)	1.8	0.3	3.6
Net benefit cost (credit) recognized for financial reporting			7.9	9.5	16.7	19
Total contributions to the pension plans during the period		$ 50
Pension Plan [Member] | Xcel Energy Inc.
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Total contributions to the pension plans during the period		$ 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	0.1	0.2
Interest cost	[1]		3.2	3.9	6.4	7.8
Expected return on plan assets	[1]		(4.4)	(4.7)	(8.7)	(9.4)
Amortization of prior service credit	[1]		(1)	(1.3)	(1.9)	(2.7)
Amortization of net loss	[1]		0.4	0.7	0.8	1.5
Net periodic benefit cost (credit)			(1.7)	(1.3)	(3.3)	(2.6)
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation			1	0.2	1.6	0.5
Net benefit cost (credit) recognized for financial reporting			$ (0.7)	$ (1.1)	$ (1.7)	$ (2.1)
[1]	The components of net periodic cost other than the service cost component are included in the line item “other income (expense), net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Commitments and Contingencies -

Commitments and Contingencies - MGP, Landfill and Disposal Sites (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)PeriodPlan
Gas Trading Litigation [Member]
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number | Plan	2
Other MGP, Landfill, or Disposal Sites
Loss Contingencies [Line Items]
Number of identified MGP sites under current investigation and/or remediation	2
Maximum [Member] | Denver MGP Site [Member]
Loss Contingencies [Line Items]
Future environmental investigation, remediation or mitigation | $	$ 9.3
Time period of future environmental, investigation, remediation and mitigation measures | Period	15

Commitments and Contingencies_2

Commitments and Contingencies - Environmental Requirements - Water and Waste (Details) - Federal Coal Ash Regulation	Jun. 30, 2020	Dec. 31, 2019
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 sites where monitoring results indicate potential offsite impacts to groundwater	1
Number of impoundments where closure plans will be expedited		1

Commitments and Contingencies_3

Commitments and Contingencies - Purchased Power Agreements (Details) - MW	Jun. 30, 2020	Dec. 31, 2019
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Variable Interest Entity [Line Items]
Generating capacity under long term purchased power agreements (in MW)	1,518	1,442

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period					$ 6,996.2
Income taxes	$ 7.7		$ 10.6		25.1		$ 29.7
Accumulated other comprehensive loss at end of period	7,420.1				7,420.1
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	(23.8)		(25)		(24.1)		(25.3)
Net current period other comprehensive loss	0.3		0.3		0.6		0.6
Accumulated other comprehensive loss at end of period	(23.5)		(24.7)		(23.5)		(24.7)
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]
Income taxes	0.1		0.1		0.2		0.1
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)	[1]	(0.6)	[2]	(0.6)	[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)		(2.5)		(0.2)
Net current period other comprehensive loss	0		0		0		0
Accumulated other comprehensive loss at end of period	(2.5)		(0.2)		(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]
Income taxes	0		0		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	[1]	0	[2]	0	[2]
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(26.3)		(25.2)		(26.6)		(25.5)
Net current period other comprehensive loss	0.3		0.3		0.6		0.6
Accumulated other comprehensive loss at end of period	(26)		(24.9)		(26)		(24.9)
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)	[1]	$ (0.6)	[2]	$ (0.6)	[2]
[1]	Included in interest charges.
[2]	Included in interest charges.

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019
Segment Reporting Information [Line Items]
Net income	$ 108.1		$ 101.5		$ 236.8		$ 240.3
Regulated Operating Revenue, Electric	715.4		692.7		1,427.2		1,434.2
Regulated Operating Revenue, Gas	186.2		207.6		517.7		676.7
Unregulated Operating Revenue	9.5		9.7		22.9		22.1
Regulated and Unregulated Operating Revenue	911.1		910		1,967.8		2,133
Related Party Transaction - Electric and Gas Domestic Regulated Revenue	1.1		1.1		2.2		2.2
Electric
Segment Reporting Information [Line Items]
Net income	89		84.8		163		167.2
Revenues Including Intersegment Revenues	715.5		692.8		1,427.4		1,434.4
Natural gas
Segment Reporting Information [Line Items]
Net income	16		17.6		68.1		76.8
Revenues Including Intersegment Revenues					517.6		676.8
All Other
Segment Reporting Information [Line Items]
Net income	3.1		(0.9)		5.7		(3.7)
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	911.2	[1]	910.1	[1]	1,967.9	[2]	2,133.3	[2]
Total revenues | Electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	715.4		692.7		1,427.2		1,434.2
Total revenues | Natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	186.2		207.6		517.7		676.7
Total revenues | All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue	9.5	[1]	9.7	[1]	22.9	[2]	22.1	[2]
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	(0.1)		(0.1)		(0.1)		(0.3)
Intersegment Eliminations | Electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	$ 0.1		$ 0.1		0.2		0.2
Intersegment Eliminations | Natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas					$ (0.1)		$ 0.1
[1]	Operating revenues include $1.1 million of other affiliate revenue for the three months ended June 30, 2020 and 2019.
[2]	Operating revenues include $2.2 million of other affiliate revenue for the six months ended June 30, 2020 and 2019.

Environmental Remediation Oblig

Environmental Remediation Obligations (Details) - Maximum [Member] - Denver MGP Site [Member] $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)Period
MGP, Landfill and Disposal Sites [Line Items]
Time period of future environmental, investigation, remediation and mitigation measures | Period	15
Future environmental investigation, remediation or mitigation | $	$ 9.3

MGP, Landfill and Disposal Site

MGP, Landfill and Disposal Sites (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)
Maximum [Member] | Denver MGP Site [Member]
Site Contingency [Line Items]
Future environmental investigation, remediation or mitigation	$ 9.3

Uncategorized Items - psco-2020

Label	Element	Value
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	$ 33,400,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	$ 11,400,000