Public Service Co Of Colorado 10-Q 29 Oct 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 29, 2020
Cover [Abstract]
Entity Central Index Key	0000081018
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 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	9 Months Ended
	Sep. 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 Sept. 30, 2020 and Dec. 31, 2019; the results of operations, including the components of net income, comprehensive income and changes in stockholder’s equity for the three and nine months ended Sept. 30, 2020 and 2019; and cash flows for the nine months ended Sept. 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 Sept. 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	9 Months Ended
	Sep. 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	9 Months Ended
	Sep. 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	444.8			444.8
Total other comprehensive income	0.9				0.9
Dividends declared to parent	(301.1)			(301.1)
Contribution of capital by parent	562.8		562.8
Balance (in shares) at Sep. 30, 2019		100
Ending Balance at Sep. 30, 2019	7,005.6	$ 0	4,903.3	2,126.9	(24.6)
Balance (in shares) at Jun. 30, 2019		100
Beginning Balance at Jun. 30, 2019	6,613.1	$ 0	4,618.3	2,019.7	(24.9)
Increase (Decrease) in Stockholder's Equity
Net income	204.5			204.5
Total other comprehensive income	0.3				0.3
Dividends declared to parent	(97.3)			(97.3)
Contribution of capital by parent	285		285
Balance (in shares) at Sep. 30, 2019		100
Ending Balance at Sep. 30, 2019	$ 7,005.6	$ 0	4,903.3	2,126.9	(24.6)
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	455.2			455.2
Total other comprehensive income	0.9				0.9
Dividends declared to parent	(694.9)			(694.9)
Contribution of capital by parent	754		754
Adoption of ASC Topic 326	$ (0.7)			(0.7)
Balance (in shares) at Sep. 30, 2020	100	100
Ending Balance at Sep. 30, 2020	$ 7,510.7	$ 0	5,693.4	1,843	(25.7)
Balance (in shares) at Jun. 30, 2020		100
Beginning Balance at Jun. 30, 2020	7,420.1	$ 0	5,693.7	1,752.4	(26)
Increase (Decrease) in Stockholder's Equity
Net income	218.4			218.4
Total other comprehensive income	0.3				0.3
Dividends declared to parent	(127.8)			(127.8)
Contribution of capital by parent	$ (0.3)		(0.3)
Balance (in shares) at Sep. 30, 2020	100	100
Ending Balance at Sep. 30, 2020	$ 7,510.7	$ 0	$ 5,693.4	$ 1,843	$ (25.7)

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating revenues
Electric	$ 915.9	$ 880.7	$ 2,343.1	$ 2,314.8
Natural gas	156.4	153.9	674.1	830.7
Other	8.8	9.7	31.7	31.8
Total operating revenues	1,081.1	1,044.3	3,048.9	3,177.3
Operating expenses
Electric fuel and purchased power	299.1	284.7	828.3	829.5
Cost of natural gas sold and transported	34.7	34.3	222.1	376.7
Cost of sales — steam and other	3.7	3.5	9.7	11.9
Operating and maintenance expenses	195.9	198.4	589.7	597.9
Demand side management expenses	35.6	36.6	107.3	100.9
Depreciation and amortization	164.4	153.5	478.9	448.6
Taxes (other than income taxes)	57.9	49	166.5	154.8
Total operating expenses	791.3	760	2,402.5	2,520.3
Operating income	289.8	284.3	646.4	657
Other (expense) income, net	(0.6)	1.4	(0.8)	1.9
Allowance for funds used during construction — equity	9.5	3.8	29.5	12.9
Interest charges and financing costs
Interest charges — includes other financing costs of $1.9, $1.6, $5.4 and $4.9, respectively	60.3	59.2	183.3	176.3
Debt Related Commitment Fees and Debt Issuance Costs	1.9	1.6	5.4	4.9
Allowance for funds used during construction — debt	(4)	(2.2)	(12.5)	(7)
Total interest charges and financing costs	56.3	57	170.8	169.3
Income before income taxes	242.4	232.5	504.3	502.5
Income tax expense	24	28	49.1	57.7
Net income	$ 218.4	$ 204.5	$ 455.2	$ 444.8

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Financial Position [Abstract]
Debt Related Commitment Fees and Debt Issuance Costs	$ 1.9	$ 1.6	$ 5.4	$ 4.9

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Comprehensive income:
Net income	$ 218.4	$ 204.5	$ 455.2	$ 444.8
Derivative instruments:
Reclassification of loss to net income, net of tax of $0.1, $0.1, $0.3 and $0.3, respectively	0.3	0.3	0.9	0.9
Tax	0.1	0.1	0.3	0.3
Total other comprehensive income	0.3	0.3	0.9	0.9
Total comprehensive income	$ 218.7	$ 204.8	$ 456.1	$ 445.7

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net income	$ 455.2	$ 444.8
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	482.2	452.2
Deferred income taxes	26	24.1
Amortization of investment tax credits	(1.9)	(1.9)
Allowance for equity funds used during construction	(29.5)	(12.9)
Provision for bad debts	16.1	11.4
Net realized and unrealized hedging and derivative transactions	(11.2)	64.5
Changes in operating assets and liabilities:
Accounts receivable	(19.3)	1.7
Accrued unbilled revenues	72.1	84.8
Inventories	(11.4)	(15.1)
Other current assets	(9.6)	(12.4)
Accounts payable	(50.5)	(96)
Net regulatory assets and liabilities	31.3	72.3
Other current liabilities	(40.9)	(66.3)
Pension and other employee benefit obligations	(44.9)	(44.4)
Other, net	(5.9)	(72.4)
Net cash provided by operating activities	857.8	834.4
Investing activities
Utility capital/construction expenditures	(1,292.9)	(1,098.6)
Investments in utility money pool arrangement	(366)	(397)
Repayments from utility money pool arrangement	366	397
Net cash used in investing activities	(1,292.9)	(1,098.6)
Financing activities
Repayments of short-term borrowings, net	0	(307)
Borrowings under utility money pool arrangement	1,382	58
Repayments under utility money pool arrangement	(1,360)	(58)
Proceeds from issuance of long-term debt	734.6	928.6
Repayments of long-term debt	(400)	(400)
Capital contributions from parent	787.7	632.7
Dividends paid to parent	(703.7)	(295.4)
Other, net	(0.3)	0
Net cash provided by financing activities	440.3	558.9
Net change in cash and cash equivalents	5.2	294.7
Cash and cash equivalents at beginning of period	11.4
Cash and cash equivalents at end of period	16.6	328.1
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(183.6)	(173.4)
Cash paid for income taxes, net	(16.8)	(43.7)
Supplemental disclosure of non-cash investing and financing transactions:
Accrued property, plant and equipment additions	159	228.5
Inventory transfers to property, plant and equipment	26.4	24.4
Operating lease right-of-use assets	14.4	653.8
Allowance for equity funds used during construction	$ 29.5	$ 12.9

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents at beginning of period	$ 16.6	$ 11.4
Accounts receivable, net	324.9	303.9
Accounts receivable from affiliates	0	52.7
Accrued unbilled revenues	220.9	293.9
Total inventories	177	192
Regulatory assets	96	64
Derivative instruments	19	7.2
Prepayments and other	77.2	55.9
Total current assets	931.6	981
Property, plant and equipment, net	17,204.5	16,155
Other assets
Regulatory assets	1,053.4	1,038.1
Derivative instruments	3.1	0
Operating lease right-of-use assets	520.5	574
Other	250.9	259.4
Total other assets	1,827.9	1,871.5
Total assets	19,964	19,007.5
Current liabilities
Current portion of long-term debt	0	400
Borrowings under utility money pool arrangement	61	39
Accounts payable	414.8	573.3
Accounts payable to affiliates	60.3	43.9
Regulatory liabilities	75	69.2
Taxes accrued	186.1	202.1
Accrued interest	35.8	53.4
Dividends payable to parent	102.9	111.5
Derivative instruments	20.8	8.7
Operating lease liabilities	92.1	85.8
Other	88.8	98.8
Total current liabilities	1,137.6	1,685.7
Deferred credits and other liabilities
Deferred income taxes	1,911	1,850.8
Deferred investment tax credits	21	22.8
Regulatory liabilities	2,316.9	2,036.8
Asset retirement obligations	359.2	324
Derivative instruments	42.5	52.5
Customer advances	170.1	173.6
Pension and employee benefit obligations	165.9	211.9
Operating lease liabilities	457.2	517.6
Other	149.2	150.9
Total deferred credits and other liabilities	5,593	5,340.9
Commitments and contingencies
Capitalization
Long-term debt	$ 5,722.7	$ 4,984.7
Common Stock, Shares Authorized	100	100
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares, Outstanding	100	100
Common stock — 100 shares authorized of $0.01 par value; 100 shares outstanding at Sept. 30, 2020 and Dec. 31, 2019, respectively	$ 0	$ 0
Additional paid in capital	5,693.4	4,939.4
Retained earnings	1,843	2,083.4
Accumulated other comprehensive loss	(25.7)	(26.6)
Total common stockholder's equity	7,510.7	6,996.2
Total liabilities and stockholder's equity	$ 19,964	$ 19,007.5

Selected Balance Sheet Data

Selected Balance Sheet Data	9 Months Ended
	Sep. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 350.6 $ 324.9 Less allowance for bad debts (25.7) (21.0) Accounts receivable, net $ 324.9 $ 303.9 (Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 63.9 $ 62.6 Fuel 63.8 77.1 Natural gas 49.3 52.3 Total inventories $ 177.0 $ 192.0 (Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 15,512.7 $ 14,361.9 Natural gas plant 4,894.2 4,631.4 Common and other property 1,157.3 1,113.5 Plant to be retired (a) 286.8 259.9 Construction work in progress 613.5 912.7 Total property, plant and equipment 22,464.5 21,279.4 Less accumulated depreciation (5,260.0) (5,124.4) Property, plant and equipment, net $ 17,204.5 $ 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	9 Months Ended
	Sep. 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 Sept. 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end 61 39 Average amount outstanding 4 7 Maximum amount outstanding 71 50 Weighted average interest rate, computed on a daily basis 0.09 % 2.29 % Weighted average interest rate at period end 0.90 1.63 % Commercial Paper — Commercial paper outstanding for PSCo was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended Sept. 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 700 $ 700 Amount outstanding at period end — — Average amount outstanding — 154 Maximum amount outstanding — 432 Weighted average interest rate, computed on a daily basis N/A 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 Sept. 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 Sept. 30, 2020, PSCo had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Drawn (b) Available $ 700 $ 8 $ 692 (a) 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 Sept. 30, 2020 and Dec. 31, 2019. Long-Term Borrowings During the nine months ended Sept. 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	9 Months Ended
	Sep. 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 consisted of the following: Three Months Ended Sept. 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 344.1 $ 95.5 $ 3.1 $ 442.7 C&I 431.2 32.8 4.6 468.6 Other 11.3 — — 11.3 Total retail 786.6 128.3 7.7 922.6 Wholesale 61.2 — — 61.2 Transmission 17.8 — — 17.8 Other 13.7 24.1 — 37.8 Total revenue from contracts with customers 879.3 152.4 7.7 1,039.4 Alternative revenue and other 36.6 4.0 1.1 41.7 Total revenues $ 915.9 $ 156.4 $ 8.8 $ 1,081.1 Three Months Ended Sept. 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 315.3 $ 94.1 $ 3.1 $ 412.5 C&I 452.4 32.9 5.5 490.8 Other 11.8 — — 11.8 Total retail 779.5 127.0 8.6 915.1 Wholesale 40.3 — — 40.3 Transmission 16.4 — — 16.4 Other 8.3 21.4 — 29.7 Total revenue from contracts with customers 844.5 148.4 8.6 1,001.5 Alternative revenue and other 36.2 5.5 1.1 42.8 Total revenues $ 880.7 $ 153.9 $ 9.7 $ 1,044.3 Nine Months Ended Sept. 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 825.4 $ 430.6 $ 9.0 $ 1,265.0 C&I 1,134.7 149.7 19.4 1,303.8 Other 35.2 — — 35.2 Total retail 1,995.3 580.3 28.4 2,604.0 Wholesale 150.0 — — 150.0 Transmission 45.0 — — 45.0 Other 43.0 77.3 — 120.3 Total revenue from contracts with customers 2,233.3 657.6 28.4 2,919.3 Alternative revenue and other 109.8 16.5 3.3 129.6 Total revenues $ 2,343.1 $ 674.1 $ 31.7 $ 3,048.9 Nine Months Ended Sept. 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 771.9 $ 535.6 $ 8.4 $ 1,315.9 C&I 1,204.7 202.6 20.0 1,427.3 Other 36.1 — — 36.1 Total retail 2,012.7 738.2 28.4 2,779.3 Wholesale 126.7 — — 126.7 Transmission 41.4 — — 41.4 Other 26.4 76.3 — 102.7 Total revenue from contracts with customers 2,207.2 814.5 28.4 3,050.1 Alternative revenue and other 107.6 16.2 3.4 127.2 Total revenues $ 2,314.8 $ 830.7 $ 31.8 $ 3,177.3

Income Taxes

Income Taxes	9 Months Ended
	Sep. 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: Nine Months Ended Sept. 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 (8.5) (7.7) Plant regulatory differences (a) (4.6) (3.6) Other tax credits, net NOL & tax credit allowances (1.1) (1.3) Other (net) (0.8) (0.6) Effective income tax rate 9.7 % 11.5 % (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 Tax Loss Carryback Claims — In 2020, Xcel Energy identified certain expenses related to tax years 2009-2011 that qualify for an extended carryback claim. PSCo is not expected to accrue any income tax expense related to this adjustment. 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 2014 — 2016 July 2021 Additionally, the statute of limitations related to the federal tax loss carryback claim referenced above has been extended. Xcel Energy has recognized its best estimate of income tax expense that will result from a final resolution of this issue; however, the outcome and timing of a resolution is unknown . In 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 Office of Appeals reached an agreement and no material adjustments were required. In 2018, the IRS began an audit of tax years 2014 - 2016. In July 2020, Xcel Energy and the IRS reached an agreement and the related benefit was recognized. State Audits — PSCo is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of Sept. 30, 2020, PSCo’s earliest open tax year subject to examination by state taxing authorities under applicable statutes of limitations is 2009. As of Sept. 30, 2020, there are no state income tax audits in progress. Unrecognized Benefits — The 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) Sept. 30, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 7.1 $ 7.4 Unrecognized tax benefit — Temporary tax positions 1.3 4.6 Total unrecognized tax benefit $ 8.4 $ 12.0 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (7.0) $ (8.3) Net deferred tax liability associated with the unrecognized tax benefit amounts and related NOLs and tax credit carryforwards were $5.7 million and $5.0 million for Sept. 30, 2020 and Dec. 31, 2019, respectively. As the IRS and state audits resume, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $2.8 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) Sept. 30, 2020 Dec. 31, 2019 Payable for interest related to unrecognized tax benefits at beginning of period $ (1.1) $ (0.7) Interest benefit (expense) related to unrecognized tax benefits 1.1 (0.4) Payable for interest related to unrecognized tax benefits at end of period $ — $ (1.1) No amounts were accrued for penalties related to unrecognized tax benefits as of Sept. 30, 2020 and Dec. 31, 2019.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	9 Months Ended
	Sep. 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 Sept. 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. The classification as a regulatory asset or liability, if applicable, is based on approved regulatory recovery mechanisms. As of Sept. 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) Sept. 30, 2020 Dec. 31, 2019 Megawatt hours of electricity 18.1 9.3 Million British thermal units of natural gas 92.8 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 on 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 Sept. 30, 2020, five of PSCo’s 10 most significant counterparties for these activities, comprising $108.3 million, or 74%, of this credit exposure, had investment grade credit ratings from S&P Global Ratings, Moody’s Investor Services or Fitch Ratings. Four of the 10 most significant counterparties, comprising $22.6 million, or 15%, of this credit exposure, were not rated by these external agencies, but based on PSCo’s internal analysis, had credit quality consistent with investment grade. One of these significant counterparties, comprising $2.9 million, or 2%, of this credit exposure, had credit quality less than investment grade, based on external analysis. Eight of these significant counterparties are independent system operators, municipal or cooperative electric entities, Regional Transmission Organizations or other utilities. The impact of derivative activity: Pre-Tax Fair Value Gains (Losses) Recognized During the Period in: (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory (Assets) and Liabilities Three Months Ended Sept. 30, 2020 Other derivative instruments Natural gas commodity $ — $ 0.6 Total $ — $ 0.6 Nine Months Ended Sept. 30, 2020 Other derivative instruments Natural gas commodity $ — $ (2.2) Total $ — $ (2.2) Three Months Ended Sept. 30, 2019 Other derivative instruments Natural gas commodity $ — $ (2.2) Total $ — $ (2.2) Nine Months Ended Sept. 30, 2019 Other derivative instruments Natural gas commodity $ — $ (3.7) Total $ — $ (3.7) Pre-Tax (Gains) Losses Reclassified into Income During the Period from: Pre-Tax Gains (Losses) Recognized During the Period in Income (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory Assets and (Liabilities) Three Months Ended Sept. 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 3.2 (b) Total $ — $ — $ 3.2 Nine Months Ended Sept. 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 1.2 (a) $ — $ — Total $ 1.2 $ — $ — Other derivative instruments Commodity trading $ — $ — $ (2.1) (b) Natural gas commodity — 3.4 (c) (3.4) (c) Total $ — $ 3.4 $ (5.5) (a) Amounts are recorded to interest charges. (b) Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate. (c) Amounts for the three and nine months ended Sept. 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 nine months ended Sept. 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 Reclassified into Income During the Period from: Pre-Tax Gains (Losses) Recognized During the Period in Income (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory Assets and (Liabilities) Three Months Ended Sept. 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 0.6 (b) Total $ — $ — $ 0.6 Nine Months Ended Sept. 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 1.2 (a) $ — $ — Total $ 1.2 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 5.3 (b) Natural gas commodity — (1.3) (c) (2.1) (c) Total $ — $ (1.3) $ 3.2 (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 nine months ended Sept. 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 nine months ended Sept. 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 nine months ended Sept. 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 Sept. 30, 2020 and Dec. 31, 2019, there were $0.1 million and no derivative instruments in a liability position with such underlying contract provisions, respectively. 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 Sept. 30, 2020 and Dec. 31, 2019. Recurring Fair Value Measurements — PSCo’s derivative assets and liabilities measured at fair value on a recurring basis: Sept. 30, 2020 Dec. 31, 2019 Fair Value Fair Value Total Netting (a) Total Fair Value Fair Value Total Netting (a) Total (Millions of Dollars) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Current derivative assets Other derivative instruments: Commodity trading $ 7.0 $ 27.6 $ 1.0 $ 35.6 $ (27.0) $ 8.6 $ 1.9 $ 11.1 $ 0.9 $ 13.9 $ (10.1) $ 3.8 Natural gas commodity — 10.4 — 10.4 — 10.4 — 3.4 — 3.4 — 3.4 Total current derivative assets $ 7.0 $ 38.0 $ 1.0 $ 46.0 $ (27.0) $ 19.0 $ 1.9 $ 14.5 $ 0.9 $ 17.3 $ (10.1) $ 7.2 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 1.6 $ 9.1 $ 2.5 $ 13.2 $ (10.1) $ 3.1 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — Total noncurrent derivative assets $ 1.6 $ 9.1 $ 2.5 $ 13.2 $ (10.1) $ 3.1 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — Sept. 30, 2020 Dec. 31, 2019 Fair Value Fair Value Total Netting (a) Total Fair Value Fair Value Total Netting (a) Total (Millions of Dollars) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Current derivative liabilities Other derivative instruments: Commodity trading $ 7.0 $ 31.6 $ 6.3 $ 44.9 $ (27.0) $ 17.9 $ 1.7 $ 16.7 $ — $ 18.4 $ (13.1) $ 5.3 Natural gas commodity — 2.9 — 2.9 — 2.9 — 3.4 — 3.4 — 3.4 Total current derivative liabilities $ 7.0 $ 34.5 $ 6.3 $ 47.8 $ (27.0) $ 20.8 $ 1.7 $ 20.1 $ — $ 21.8 $ (13.1) $ 8.7 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 0.9 $ 21.4 $ 35.5 $ 57.8 $ (15.3) $ 42.5 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6) $ 52.5 Total noncurrent derivative assets $ 0.9 $ 21.4 $ 35.5 $ 57.8 $ (15.3) $ 42.5 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6) $ 52.5 (a) PSCo nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Sept. 30, 2020 and Dec. 31, 2019. At Sept. 30, 2020 and Dec. 31, 2019, derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $5.2 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 Sept. 30 (Millions of Dollars) 2020 2019 Balance at July 1 $ (17.1) $ 0.2 Settlements 0.5 (0.5) Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (21.7) 0.5 Balance at Sept. 30 $ (38.3) $ 0.2 Nine Months Ended Sept. 30 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ (12.7) $ 0.1 Settlements (0.6) (1.4) Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (25.0) 1.5 Balance at Sept. 30 $ (38.3) $ 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 nine months ended Sept. 30, 2020 and 2019. Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: Sept. 30, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 5,722.7 $ 6,932.2 $ 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 Sept. 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	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost (Credit) Three Months Ended Sept. 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) Effects of regulation 2.9 0.8 0.6 0.4 Net benefit cost (credit) recognized for financial reporting $ 11.1 $ 8.5 $ (1.1) $ (0.9) Nine Months Ended Sept. 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 22.9 $ 19.2 $ 0.2 $ 0.4 Interest cost (a) 34.3 38.7 9.5 11.7 Expected return on plan assets (a) (52.9) (51.4) (13.1) (14.2) Amortization of prior service credit (a) (2.1) (2.5) (2.8) (4.1) Amortization of net loss (a) 22.4 19.1 1.2 2.2 Net periodic benefit cost (credit) 24.6 23.1 (5.0) (4.0) Effects of regulation 3.3 4.4 2.2 0.9 Net benefit cost (credit) recognized for financial reporting $ 27.9 $ 27.5 $ (2.8) $ (3.1) (a) The components of net periodic cost other than the service cost component are included in the line item “Other (expense) income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets 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	9 Months Ended
	Sep. 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 Inc., 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 currently investigating, remediating or performing post-closure actions at three 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. Groundwater monitoring consistent with the CCR Rule continued in 2020. Statistically significant increases 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. On Aug. 28, 2020, the EPA published its final rule to implement a cease receipt and initiate a closure date of April 11, 2021 for all CCR impoundments affected by an August 2018 D.C. Circuit ruling. The D.C. Circuit concluded that the EPA cannot allow utilities to continue to use unlined impoundments (including clay lined impoundments) for the storage or disposal of coal ash. PSCo is pursuing options to provide alternative storage capacity consistent with the CCR Rule at one facility until the affected generating units are retired in 2025. Closure costs for existing impoundments are included in the calculation of the asset retirement obligation. 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 Sept. 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. The PPAs have expiration dates through 2032.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity Note [Abstract]
Other Comprehensive Income	Changes in accumulated other comprehensive loss, net of tax, for the three and nine months ended Sept. 30, 2020 and 2019: Three Months Ended Sept. 30, 2020 Three Months Ended Sept. 30, 2019 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at July 1 $ (23.5) $ (2.5) $ (26.0) $ (24.7) $ (0.2) $ (24.9) 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 Sept. 30 $ (23.2) $ (2.5) $ (25.7) $ (24.4) $ (0.2) $ (24.6) (a) Included in interest charges. Nine Months Ended Sept. 30, 2020 Nine Months Ended Sept. 30, 2019 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (24.1) $ (2.5) $ (26.6) $ (25.3) $ (0.2) $ (25.5) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.3, $—, $0.3 and $—, respectively) (a) 0.9 — 0.9 0.9 — 0.9 Net current period other comprehensive income 0.9 — 0.9 0.9 — 0.9 Accumulated other comprehensive loss at Sept. 30 $ (23.2) $ (2.5) $ (25.7) $ (24.4) $ (0.2) $ (24.6) (a) Included in interest charges.

Segment Information

Segment Information	9 Months Ended
	Sep. 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. • 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 nine months ended Sept. 30: Three Months Ended Sept. 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 915.9 $ 880.7 Intersegment revenue 0.1 0.1 Total revenues $ 916.0 $ 880.8 Net income 214.5 204.7 Regulated Natural Gas Operating revenues $ 156.4 $ 153.9 Intersegment revenue 0.1 0.1 Total revenues $ 156.5 $ 154.0 Net income 4.4 0.7 All Other Operating revenues (a) $ 8.8 $ 9.7 Net loss (0.5) (0.9) Consolidated Total Operating revenues (a) $ 1,081.3 $ 1,044.5 Reconciling eliminations (0.2) (0.2) Total operating revenues $ 1,081.1 $ 1,044.3 Net income 218.4 204.5 (a) Operating revenues include $1.1 million of other affiliate revenue for the three months ended Sept. 30, 2020 and 2019. Nine Months Ended Sept. 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 2,343.1 $ 2,314.8 Intersegment revenue 0.3 0.3 Total revenues $ 2,343.4 $ 2,315.1 Net income 377.5 371.9 Regulated Natural Gas Operating revenues $ 674.1 $ 830.7 Intersegment revenues — 0.2 Total revenues $ 674.1 $ 830.9 Net income 72.5 77.5 All Other Operating revenues (a) $ 31.7 $ 31.8 Net income (loss) 5.2 (4.6) Consolidated Total Operating revenues (a) $ 3,049.2 $ 3,177.8 Reconciling eliminations (0.3) (0.5) Total operating revenues $ 3,048.9 $ 3,177.3 Net income 455.2 444.8 (a) Operating revenues include $3.3 million of other affiliate revenue for the nine months ended Sept. 30, 2020 and 2019.

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	9 Months Ended
	Sep. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 350.6 $ 324.9 Less allowance for bad debts (25.7) (21.0) Accounts receivable, net $ 324.9 $ 303.9
Inventories	(Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 63.9 $ 62.6 Fuel 63.8 77.1 Natural gas 49.3 52.3 Total inventories $ 177.0 $ 192.0
Property, Plant and Equipment, Net	(Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Property, plant and equipment, net Electric plant $ 15,512.7 $ 14,361.9 Natural gas plant 4,894.2 4,631.4 Common and other property 1,157.3 1,113.5 Plant to be retired (a) 286.8 259.9 Construction work in progress 613.5 912.7 Total property, plant and equipment 22,464.5 21,279.4 Less accumulated depreciation (5,260.0) (5,124.4) Property, plant and equipment, net $ 17,204.5 $ 16,155.0

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	9 Months Ended
	Sep. 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 Sept. 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 700 $ 700 Amount outstanding at period end — — Average amount outstanding — 154 Maximum amount outstanding — 432 Weighted average interest rate, computed on a daily basis N/A 2.67 % Weighted average interest rate at period end N/A N/A
Credit Facilities	At Sept. 30, 2020, PSCo had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Drawn (b) Available $ 700 $ 8 $ 692 (a) 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 Sept. 30, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end 61 39 Average amount outstanding 4 7 Maximum amount outstanding 71 50 Weighted average interest rate, computed on a daily basis 0.09 % 2.29 % Weighted average interest rate at period end 0.90 1.63 %

Revenues (Tables)

Revenues (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	PSCo’s operating revenues consisted of the following: Three Months Ended Sept. 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 344.1 $ 95.5 $ 3.1 $ 442.7 C&I 431.2 32.8 4.6 468.6 Other 11.3 — — 11.3 Total retail 786.6 128.3 7.7 922.6 Wholesale 61.2 — — 61.2 Transmission 17.8 — — 17.8 Other 13.7 24.1 — 37.8 Total revenue from contracts with customers 879.3 152.4 7.7 1,039.4 Alternative revenue and other 36.6 4.0 1.1 41.7 Total revenues $ 915.9 $ 156.4 $ 8.8 $ 1,081.1 Three Months Ended Sept. 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 315.3 $ 94.1 $ 3.1 $ 412.5 C&I 452.4 32.9 5.5 490.8 Other 11.8 — — 11.8 Total retail 779.5 127.0 8.6 915.1 Wholesale 40.3 — — 40.3 Transmission 16.4 — — 16.4 Other 8.3 21.4 — 29.7 Total revenue from contracts with customers 844.5 148.4 8.6 1,001.5 Alternative revenue and other 36.2 5.5 1.1 42.8 Total revenues $ 880.7 $ 153.9 $ 9.7 $ 1,044.3 Nine Months Ended Sept. 30, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 825.4 $ 430.6 $ 9.0 $ 1,265.0 C&I 1,134.7 149.7 19.4 1,303.8 Other 35.2 — — 35.2 Total retail 1,995.3 580.3 28.4 2,604.0 Wholesale 150.0 — — 150.0 Transmission 45.0 — — 45.0 Other 43.0 77.3 — 120.3 Total revenue from contracts with customers 2,233.3 657.6 28.4 2,919.3 Alternative revenue and other 109.8 16.5 3.3 129.6 Total revenues $ 2,343.1 $ 674.1 $ 31.7 $ 3,048.9 Nine Months Ended Sept. 30, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 771.9 $ 535.6 $ 8.4 $ 1,315.9 C&I 1,204.7 202.6 20.0 1,427.3 Other 36.1 — — 36.1 Total retail 2,012.7 738.2 28.4 2,779.3 Wholesale 126.7 — — 126.7 Transmission 41.4 — — 41.4 Other 26.4 76.3 — 102.7 Total revenue from contracts with customers 2,207.2 814.5 28.4 3,050.1 Alternative revenue and other 107.6 16.2 3.4 127.2 Total revenues $ 2,314.8 $ 830.7 $ 31.8 $ 3,177.3

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 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: Nine Months Ended Sept. 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 (8.5) (7.7) Plant regulatory differences (a) (4.6) (3.6) Other tax credits, net NOL & tax credit allowances (1.1) (1.3) Other (net) (0.8) (0.6) Effective income tax rate 9.7 % 11.5 % (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 2014 — 2016 July 2021
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 7.1 $ 7.4 Unrecognized tax benefit — Temporary tax positions 1.3 4.6 Total unrecognized tax benefit $ 8.4 $ 12.0
Tax Benefits Associated with NOL and Tax Credit Carryforwards	Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (7.0) $ (8.3)
Interest Payable related to Unrecognized Tax Benefits [Table Text Block]	Interest payable related to unrecognized tax benefits: (Millions of Dollars) Sept. 30, 2020 Dec. 31, 2019 Payable for interest related to unrecognized tax benefits at beginning of period $ (1.1) $ (0.7) Interest benefit (expense) related to unrecognized tax benefits 1.1 (0.4) Payable for interest related to unrecognized tax benefits at end of period $ — $ (1.1)

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 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) Sept. 30, 2020 Dec. 31, 2019 Megawatt hours of electricity 18.1 9.3 Million British thermal units of natural gas 92.8 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 Gains (Losses) Recognized During the Period in: (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory (Assets) and Liabilities Three Months Ended Sept. 30, 2020 Other derivative instruments Natural gas commodity $ — $ 0.6 Total $ — $ 0.6 Nine Months Ended Sept. 30, 2020 Other derivative instruments Natural gas commodity $ — $ (2.2) Total $ — $ (2.2) Three Months Ended Sept. 30, 2019 Other derivative instruments Natural gas commodity $ — $ (2.2) Total $ — $ (2.2) Nine Months Ended Sept. 30, 2019 Other derivative instruments Natural gas commodity $ — $ (3.7) Total $ — $ (3.7) Pre-Tax (Gains) Losses Reclassified into Income During the Period from: Pre-Tax Gains (Losses) Recognized During the Period in Income (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory Assets and (Liabilities) Three Months Ended Sept. 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 3.2 (b) Total $ — $ — $ 3.2 Nine Months Ended Sept. 30, 2020 Derivatives designated as cash flow hedges Interest rate $ 1.2 (a) $ — $ — Total $ 1.2 $ — $ — Other derivative instruments Commodity trading $ — $ — $ (2.1) (b) Natural gas commodity — 3.4 (c) (3.4) (c) Total $ — $ 3.4 $ (5.5) (a) Amounts are recorded to interest charges. (b) Amounts are recorded to electric operating revenues. Portions of these gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue as appropriate. (c) Amounts for the three and nine months ended Sept. 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 nine months ended Sept. 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 Reclassified into Income During the Period from: Pre-Tax Gains (Losses) Recognized During the Period in Income (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory Assets and (Liabilities) Three Months Ended Sept. 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 0.4 (a) $ — $ — Total $ 0.4 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 0.6 (b) Total $ — $ — $ 0.6 Nine Months Ended Sept. 30, 2019 Derivatives designated as cash flow hedges Interest rate $ 1.2 (a) $ — $ — Total $ 1.2 $ — $ — Other derivative instruments Commodity trading $ — $ — $ 5.3 (b) Natural gas commodity — (1.3) (c) (2.1) (c) Total $ — $ (1.3) $ 3.2 (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	Sept. 30, 2020 Dec. 31, 2019 Fair Value Fair Value Total Netting (a) Total Fair Value Fair Value Total Netting (a) Total (Millions of Dollars) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Current derivative assets Other derivative instruments: Commodity trading $ 7.0 $ 27.6 $ 1.0 $ 35.6 $ (27.0) $ 8.6 $ 1.9 $ 11.1 $ 0.9 $ 13.9 $ (10.1) $ 3.8 Natural gas commodity — 10.4 — 10.4 — 10.4 — 3.4 — 3.4 — 3.4 Total current derivative assets $ 7.0 $ 38.0 $ 1.0 $ 46.0 $ (27.0) $ 19.0 $ 1.9 $ 14.5 $ 0.9 $ 17.3 $ (10.1) $ 7.2 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 1.6 $ 9.1 $ 2.5 $ 13.2 $ (10.1) $ 3.1 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — Total noncurrent derivative assets $ 1.6 $ 9.1 $ 2.5 $ 13.2 $ (10.1) $ 3.1 $ 0.4 $ 8.1 $ 1.1 $ 9.6 $ (9.6) $ — Sept. 30, 2020 Dec. 31, 2019 Fair Value Fair Value Total Netting (a) Total Fair Value Fair Value Total Netting (a) Total (Millions of Dollars) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Current derivative liabilities Other derivative instruments: Commodity trading $ 7.0 $ 31.6 $ 6.3 $ 44.9 $ (27.0) $ 17.9 $ 1.7 $ 16.7 $ — $ 18.4 $ (13.1) $ 5.3 Natural gas commodity — 2.9 — 2.9 — 2.9 — 3.4 — 3.4 — 3.4 Total current derivative liabilities $ 7.0 $ 34.5 $ 6.3 $ 47.8 $ (27.0) $ 20.8 $ 1.7 $ 20.1 $ — $ 21.8 $ (13.1) $ 8.7 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 0.9 $ 21.4 $ 35.5 $ 57.8 $ (15.3) $ 42.5 $ 0.4 $ 47.0 $ 14.7 $ 62.1 $ (9.6) $ 52.5 Total noncurrent derivative assets $ 0.9 $ 21.4 $ 35.5 $ 57.8 $ (15.3) $ 42.5 $ 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 Sept. 30 (Millions of Dollars) 2020 2019 Balance at July 1 $ (17.1) $ 0.2 Settlements 0.5 (0.5) Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (21.7) 0.5 Balance at Sept. 30 $ (38.3) $ 0.2 Nine Months Ended Sept. 30 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ (12.7) $ 0.1 Settlements (0.6) (1.4) Net transactions recorded during the period: (Losses) gains recognized in earnings (a) (25.0) 1.5 Balance at Sept. 30 $ (38.3) $ 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: Sept. 30, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 5,722.7 $ 6,932.2 $ 5,384.7 $ 6,039.3

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost (Credit)	Components of Net Periodic Benefit Cost (Credit) Three Months Ended Sept. 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) Effects of regulation 2.9 0.8 0.6 0.4 Net benefit cost (credit) recognized for financial reporting $ 11.1 $ 8.5 $ (1.1) $ (0.9) Nine Months Ended Sept. 30 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Service cost $ 22.9 $ 19.2 $ 0.2 $ 0.4 Interest cost (a) 34.3 38.7 9.5 11.7 Expected return on plan assets (a) (52.9) (51.4) (13.1) (14.2) Amortization of prior service credit (a) (2.1) (2.5) (2.8) (4.1) Amortization of net loss (a) 22.4 19.1 1.2 2.2 Net periodic benefit cost (credit) 24.6 23.1 (5.0) (4.0) Effects of regulation 3.3 4.4 2.2 0.9 Net benefit cost (credit) recognized for financial reporting $ 27.9 $ 27.5 $ (2.8) $ (3.1) (a) The components of net periodic cost other than the service cost component are included in the line item “Other (expense) income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets 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 (expense) income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset.

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 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 nine months ended Sept. 30, 2020 and 2019: Three Months Ended Sept. 30, 2020 Three Months Ended Sept. 30, 2019 (Millions of Dollars) Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Gains and Losses on Cash Flow Hedges Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at July 1 $ (23.5) $ (2.5) $ (26.0) $ (24.7) $ (0.2) $ (24.9) 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 Sept. 30 $ (23.2) $ (2.5) $ (25.7) $ (24.4) $ (0.2) $ (24.6)

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Results from Operations by Reportable Segment	PSCo’s segment information for the three and nine months ended Sept. 30: Three Months Ended Sept. 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 915.9 $ 880.7 Intersegment revenue 0.1 0.1 Total revenues $ 916.0 $ 880.8 Net income 214.5 204.7 Regulated Natural Gas Operating revenues $ 156.4 $ 153.9 Intersegment revenue 0.1 0.1 Total revenues $ 156.5 $ 154.0 Net income 4.4 0.7 All Other Operating revenues (a) $ 8.8 $ 9.7 Net loss (0.5) (0.9) Consolidated Total Operating revenues (a) $ 1,081.3 $ 1,044.5 Reconciling eliminations (0.2) (0.2) Total operating revenues $ 1,081.1 $ 1,044.3 Net income 218.4 204.5 (a) Operating revenues include $1.1 million of other affiliate revenue for the three months ended Sept. 30, 2020 and 2019. Nine Months Ended Sept. 30 (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues $ 2,343.1 $ 2,314.8 Intersegment revenue 0.3 0.3 Total revenues $ 2,343.4 $ 2,315.1 Net income 377.5 371.9 Regulated Natural Gas Operating revenues $ 674.1 $ 830.7 Intersegment revenues — 0.2 Total revenues $ 674.1 $ 830.9 Net income 72.5 77.5 All Other Operating revenues (a) $ 31.7 $ 31.8 Net income (loss) 5.2 (4.6) Consolidated Total Operating revenues (a) $ 3,049.2 $ 3,177.8 Reconciling eliminations (0.3) (0.5) Total operating revenues $ 3,048.9 $ 3,177.3 Net income 455.2 444.8	[1],[2]
[1]	Operating revenues include $1.1 million of other affiliate revenue for the three months ended Sept. 30, 2020 and 2019.
[2]	Operating revenues include $3.3 million of other affiliate revenue for the nine months ended Sept. 30, 2020 and 2019.

Accounting Pronouncements (Deta

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

Selected Balance Sheet Data (De

Selected Balance Sheet Data (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts receivable, net
Accounts receivable	$ 350.6	$ 324.9
Less allowance for bad debts	(25.7)	(21)
Accounts receivable, net	$ 324.9	$ 303.9

Selected Balance Sheet Data Bal

Selected Balance Sheet Data Balance Sheet Related Disclosures, Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Public Utilities, Inventory [Line Items]
Total inventories	$ 177	$ 192
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	63.9	62.6
Fuel
Public Utilities, Inventory [Line Items]
Inventories	63.8	77.1
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 49.3	$ 52.3

Selected Balance Sheet Data B_2

Selected Balance Sheet Data Balance Sheet Related Disclosures, Property, Plant and Equipment (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 22,464.5	$ 21,279.4
Less accumulated depreciation		(5,260)	(5,124.4)
Property, plant and equipment, net		17,204.5	16,155
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		15,512.7	14,361.9
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		4,894.2	4,631.4
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		1,157.3	1,113.5
Plant to be retired
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	[1]	286.8	259.9
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 613.5	$ 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.

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments - Short-Term Borrowings (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Money Pool
Short-term Debt [Line Items]
Borrowing limit	$ 250,000,000	$ 250,000,000
Short-term Debt	61,000,000	39,000,000
Average amount outstanding	4,000,000	7,000,000
Maximum amount outstanding	$ 71,000,000	$ 50,000,000
Weighted average interest rate, computed on a daily basis (percentage)	0.09%	2.29%
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.90%	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	0	154,000,000
Maximum amount outstanding	$ 0	$ 432,000,000
Weighted average interest rate, computed on a daily basis (percentage)		2.67%

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments - Letters of Credit (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 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)		9 Months Ended
		Sep. 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]	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 ($)	9 Months Ended
	Sep. 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	$ 1,039.4	$ 1,001.5	$ 2,919.3	$ 3,050.1
Retail
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	922.6	915.1	2,604	2,779.3
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	442.7	412.5	1,265	1,315.9
Retail | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	468.6	490.8	1,303.8	1,427.3
Retail | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	11.3	11.8	35.2	36.1
Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	61.2	40.3	150	126.7
Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	17.8	16.4	45	41.4
Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	37.8	29.7	120.3	102.7
Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	41.7	42.8	129.6	127.2
Regulated Electric | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	879.3	844.5	2,233.3	2,207.2
Regulated Electric | Retail
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	786.6	779.5	1,995.3	2,012.7
Regulated Electric | Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	344.1	315.3	825.4	771.9
Regulated Electric | Retail | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	431.2	452.4	1,134.7	1,204.7
Regulated Electric | Retail | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	11.3	11.8	35.2	36.1
Regulated Electric | Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	61.2	40.3	150	126.7
Regulated Electric | Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	17.8	16.4	45	41.4
Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	13.7	8.3	43	26.4
Regulated Electric | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	36.6	36.2	109.8	107.6
Regulated Natural Gas | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	152.4	148.4	657.6	814.5
Regulated Natural Gas | Retail
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	128.3	127	580.3	738.2
Regulated Natural Gas | Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	95.5	94.1	430.6	535.6
Regulated Natural Gas | Retail | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	32.8	32.9	149.7	202.6
Regulated Natural Gas | Retail | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
Regulated Natural Gas | Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
Regulated Natural Gas | Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	24.1	21.4	77.3	76.3
Regulated Natural Gas | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	4	5.5	16.5	16.2
All Other | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	7.7	8.6	28.4	28.4
All Other | Retail
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	7.7	8.6	28.4	28.4
All Other | Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	3.1	3.1	9	8.4
All Other | Retail | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	4.6	5.5	19.4	20
All Other | Retail | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
All Other | Wholesale Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
All Other | Transmission Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
All Other | Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0	0	0	0
All Other | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	1.1	1.1	3.3	3.4
Total revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	1,081.1	1,044.3	3,048.9	3,177.3
Total revenues | Regulated Electric
Disaggregation of Revenue [Line Items]
Total operating revenues	915.9	880.7	2,343.1	2,314.8
Total revenues | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Total operating revenues	156.4	153.9	674.1	830.7
Total revenues | All Other
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 8.8	$ 9.7	$ 31.7	$ 31.8

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits			$ 8.4		$ 12
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			(8.50%)	(7.70%)
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[1]		(4.60%)	(3.60%)
Regulatory differences - reversal of prior quarters' ARAM deferral (b)			(1.10%)	(1.30%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent			(0.80%)	(0.60%)
Effective Income Tax Rate Reconciliation, Percent			9.70%	11.50%
Federal income tax adjustment			$ 0
State income tax adjustment			0
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit — Permanent tax positions			7.1		7.4
Unrecognized tax benefit — Temporary tax positions			1.3		4.6
Total unrecognized tax benefit			8.4		12
NOL and tax credit carryforwards			(7)		(8.3)
Net Deferred Tax Liability associated with the Unrecognized Tax Benefit Amounts and Related NOLs and Tax Credit Carryforwards			(5.7)		(5)
Upper bound of decrease in unrecognized tax benefit that is reasonably possible			2.8
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		$ (1.1)	(1.1)	$ (0.7)
Interest benefit (expense) related to unrecognized tax benefits		$ (0.4)	(1.1)
Payable for interest related to unrecognized tax benefits at end of period			$ 0
[1]	Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions.

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) $ in Millions	Sep. 30, 2020USD ($)
Interest Rate Swap
Derivative [Line Items]
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

Commodity Derivatives (Details)

Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Sep. 30, 2020USD ($)MWhMMBTU	Dec. 31, 2019MWhMMBTU
cash flow hedge commodity [Member]
Derivative [Line Items]
Commodity contracts designated as cash flow hedges | $		$ 0
Electric Commodity (in megawatt hours)
Derivative [Line Items]
Derivative, Nonmonetary Notional amount | MWh	[1],[2]	18.1	9.3
Natural Gas Commodity (in million British thermal units)
Derivative [Line Items]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	92.8	32.2
[1]	Amounts are not reflective of net positions in the underlying commodities.
[2]	Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

Consideration of Credit Risk an

Consideration of Credit Risk and Concentrations (Details) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020USD ($)Counterparty		Sep. 30, 2019USD ($)		Sep. 30, 2020USD ($)Counterparty		Sep. 30, 2019USD ($)
Consideration of Credit Risk and Concentrations [Abstract]
Derivative instruments designated as fair value hedges	$ 0		$ 0		$ 0		$ 0
Other Derivative Instruments
Consideration of Credit Risk and Concentrations [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	0.6		(2.2)		(2.2)		(3.7)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	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	3.2		0.6		(5.5)		3.2
Other Derivative Instruments | Natural Gas Commodity
Consideration of Credit Risk and Concentrations [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	0.6		(2.2)		(2.2)		(3.7)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net					0		0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)					(3.4)	[1]	(1.3)	[2]
Pre-tax gains (losses) recognized during the period in income					(3.4)	[1]	(2.1)	[2]
Other Derivative Instruments | Commodity Trading
Consideration of Credit Risk and Concentrations [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	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	3.2	[3]	0.6	[4]	(2.1)	[3]	5.3	[4]
Other Derivative Instruments | Natural Gas [Member]
Consideration of Credit Risk and Concentrations [Abstract]
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities	0		0		0		0
Designated as Hedging Instrument | Cash Flow Hedges
Consideration of Credit Risk and Concentrations [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0.4		0.4		1.2		1.2
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
Designated as Hedging Instrument | Interest Rate | Cash Flow Hedges
Consideration of Credit Risk and Concentrations [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0.4	[5]	0.4	[6]	1.2	[5]	1.2	[6]
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
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				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	8				8
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				5
Wholesale, trading and non-trading commodity credit exposure for the most significant counterparties	$ 108.3				$ 108.3
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)	74.00%				74.00%
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	4				4
Wholesale, trading and non-trading commodity credit exposure for the most significant counterparties	$ 22.6				$ 22.6
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)	15.00%				15.00%
Credit Concentration Risk | External Credit Rating, Non 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	1				1
Wholesale, trading and non-trading commodity credit exposure for the most significant counterparties	$ 2.9				$ 2.9
Percentage of wholesale, trading and non-trading commodity credit exposure for the most significant counterparties (in hundredths)	2.00%				2.00%
[1]	Amounts for the three and nine months ended Sept. 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 nine months ended Sept. 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.
[2]	Amounts for the three and nine months ended Sept. 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 nine months ended Sept. 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.
[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 are recorded to interest charges.
[6]	Amounts are recorded to interest charges.

Credit Related Contingent Featu

Credit Related Contingent Features (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Derivative instruments in a gross liability position	$ 0.1	$ 0
Collateral posted related to adequate assurance clauses in derivative contracts	$ 0	$ 0

Recurring Fair Value Measuremen

Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Return Cash Collateral		$ 0	$ 0
Reclaim Cash Collateral		5.2	3
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		46	17.3
Netting	[1]	(27)	(10.1)
Derivative Asset, Net		19	7.2
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		7	1.9
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		38	14.5
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		1	0.9
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		35.6	13.9
Netting	[1]	(27)	(10.1)
Derivative Asset, Net		8.6	3.8
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		10.4	3.4
Netting	[1]	0	0
Derivative Asset, Net		10.4	3.4
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		7	1.9
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 1 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		27.6	11.1
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 2 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		10.4	3.4
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		1	0.9
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 3 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		13.2	9.6
Netting	[1]	(10.1)	(9.6)
Derivative Asset, Net		3.1	0
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		1.6	0.4
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		9.1	8.1
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		2.5	1.1
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		13.2	9.6
Netting	[1]	(10.1)	(9.6)
Derivative Asset, Net		3.1	0
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		1.6	0.4
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		9.1	8.1
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		2.5	1.1
Fair Value Measured on a Recurring Basis | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		47.8	21.8
Netting	[1]	(27)	(13.1)
Derivative Liability, Net		20.8	8.7
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		7	1.7
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		34.5	20.1
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		6.3	0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		44.9	18.4
Netting	[1]	(27)	(13.1)
Derivative Liability, Net		17.9	5.3
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		2.9	3.4
Netting	[1]	0	0
Derivative Liability, Net		2.9	3.4
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		7	1.7
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 1 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		31.6	16.7
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 2 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		2.9	3.4
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		6.3	0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 3 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		57.8	62.1
Netting	[1]	(15.3)	(9.6)
Derivative Liability, Net		42.5	52.5
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0.9	0.4
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		21.4	47
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		35.5	14.7
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		57.8	62.1
Netting	[1]	(15.3)	(9.6)
Derivative Liability, Net		42.5	52.5
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		0.9	0.4
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		21.4	47
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Gross		$ 35.5	$ 14.7
[1]	PSCo nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Sept. 30, 2020 and Dec. 31, 2019. At Sept. 30, 2020 and Dec. 31, 2019, derivative liabilities include no obligations to return cash collateral and the right to reclaim cash collateral of $5.2 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 De

Changes in Level 3 Commodity Derivatives (Details) - Commodity Contract - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ (17.1)	$ 0.2	$ (12.7)	$ 0.1
Settlements		0.5	(0.5)	(0.6)	(1.4)
(Losses) gains recognized in earnings	[1]	(21.7)	0.5	(25)	1.5
Ending Balance		(38.3)	0.2	(38.3)	0.2
Transfers Level 3, Net		$ 0	$ 0	$ 0	$ 0
[1]	Amounts relate to commodity derivatives held at the end of the period.

Fair Value of Long-Term Debt (D

Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 5,722.7	$ 5,384.7
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value	$ 6,932.2	$ 6,039.3

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
		Jan. 31, 2020USD ($)Plan	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			$ 7.6	$ 6.4	$ 22.9	$ 19.2
Interest Cost	[1]		11.4	12.9	34.3	38.7
Expected return on Plan Assets	[1]		(17.6)	(17.1)	(52.9)	(51.4)
Amortization of prior service credit	[1]		(0.7)	(0.8)	(2.1)	(2.5)
Amortization of net loss	[1]		7.5	6.3	22.4	19.1
Net periodic benefit cost (credit)			8.2	7.7	24.6	23.1
Effects of regulation			2.9	0.8	3.3	4.4
Net benefit cost (credit) recognized for financial reporting			11.1	8.5	27.9	27.5
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	0.2	0.4
Interest Cost	[1]		3.2	3.9	9.5	11.7
Expected return on Plan Assets	[1]		(4.4)	(4.7)	(13.1)	(14.2)
Amortization of prior service credit	[1]		(1)	(1.3)	(2.8)	(4.1)
Amortization of net loss	[1]		0.4	0.7	1.2	2.2
Net periodic benefit cost (credit)			(1.7)	(1.3)	(5)	(4)
Effects of regulation			0.6	0.4	2.2	0.9
Net benefit cost (credit) recognized for financial reporting			$ (1.1)	$ (0.9)	$ (2.8)	$ (3.1)
[1]	The components of net periodic cost other than the service cost component are included in the line item “Other (expense) income, net” in the consolidated statements of income or capitalized on the consolidated balance sheets as a regulatory asset.

Gas Trading Litigation (Details

Gas Trading Litigation (Details)	Sep. 30, 2020Plan
Gas Trading Litigation [Member]
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number	2

Commitments and Contingencies -

Commitments and Contingencies - MGP, Landfill and Disposal Sites (Details)	Sep. 30, 2020
Other MGP, Landfill, or Disposal Sites
Loss Contingencies [Line Items]
Number of identified MGP sites under current investigation and/or remediation	3

Commitments and Contingencies_2

Commitments and Contingencies - Environmental Requirements - Water and Waste (Details)	Sep. 30, 2020	Dec. 31, 2019
Federal Coal Ash Regulation
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
Federal Coal Ash Regulation [Domain]
Site Contingency [Line Items]
Number of facilities where alternative storage capacity options consistent with the CCR Rule are being pursued	1

Commitments and Contingencies_3

Commitments and Contingencies - Variable Interest Entities (Details) - MW	Sep. 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				9 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period					$ 6,996.2
Income Tax Expense (Benefit)	$ 24		$ 28		49.1		$ 57.7
Accumulated other comprehensive loss at end of period	7,510.7				7,510.7
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	(23.5)		(24.7)		(24.1)		(25.3)
Net current period other comprehensive loss	0.3		0.3		0.9		0.9
Accumulated other comprehensive loss at end of period	(23.2)		(24.4)		(23.2)		(24.4)
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 Tax Expense (Benefit)	0.1		0.1		0.3		0.3
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]	(0.9)	[2]	(0.9)	[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 Tax Expense (Benefit)	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)		(24.9)		(26.6)		(25.5)
Net current period other comprehensive loss	0.3		0.3		0.9		0.9
Accumulated other comprehensive loss at end of period	(25.7)		(24.6)		(25.7)		(24.6)
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]	$ (0.9)	[2]	$ (0.9)	[2]
[1]	Included in interest charges.
[2]	Included in interest charges.

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019
Segment Reporting Information [Line Items]
Net income	$ 218.4		$ 204.5		$ 455.2		$ 444.8
Regulated Operating Revenue, Electric	915.9		880.7		2,343.1		2,314.8
Regulated Operating Revenue, Gas	156.4		153.9		674.1		830.7
Unregulated Operating Revenue	8.8		9.7		31.7		31.8
Regulated and Unregulated Operating Revenue	1,081.1		1,044.3		3,048.9		3,177.3
Affiliate Revenue	1.1		1.1		3.3		3.3
Electric
Segment Reporting Information [Line Items]
Net income	214.5		204.7		377.5		371.9
Revenues Including Intersegment Revenues	916		880.8		2,343.4		2,315.1
Natural gas
Segment Reporting Information [Line Items]
Net income	4.4		0.7		72.5		77.5
Revenues Including Intersegment Revenues	156.5		154		674.1		830.9
All Other
Segment Reporting Information [Line Items]
Net income	(0.5)		(0.9)		5.2		(4.6)
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	1,081.3	[1]	1,044.5	[1]	3,049.2	[2]	3,177.8	[2]
Total revenues | Electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	915.9		880.7		2,343.1		2,314.8
Total revenues | Natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	156.4		153.9		674.1		830.7
Total revenues | All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue	8.8	[3]	9.7	[1]	31.7	[2]	31.8	[2]
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	(0.2)		(0.2)		(0.3)		(0.5)
Intersegment Eliminations | Electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	0.1		0.1		0.3		0.3
Intersegment Eliminations | Natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	$ 0.1		$ 0.1		$ 0		$ 0.2
[1]	Operating revenues include $1.1 million of other affiliate revenue for the three months ended Sept. 30, 2020 and 2019.
[2]	Operating revenues include $3.3 million of other affiliate revenue for the nine months ended Sept. 30, 2020 and 2019.
[3]	Operating revenues include $1.1 million of other affiliate revenue for the three months ended Sept. 30, 2020 and 2019.