Northern States Power 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 07, 2020
Cover [Abstract]
Entity Registrant Name	NORTHERN STATES POWER CO
Entity Central Index Key	0001123852
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-31387
Entity Tax Identification Number	41-1967505
Entity Incorporation, State or Country Code	MN
Entity Address, Address Line One	414 Nicollet Mall
Entity Address, City or Town	Minneapolis
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55401
City Area Code	612
Local Phone Number	330-5500
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		1,000,000

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2018		1,000,000
Beginning balance at Dec. 31, 2018	$ 5,573.1	$ 0	$ 3,624.2	$ 1,972	$ (23.1)
Increase (Decrease) in Stockholders' Equity
Net income	113.2			113.2
Other comprehensive income	0.2				0.2
Dividends declared on common stock	(94.6)			(94.6)
Contribution of capital by parent	170		170
Balance (in shares) at Mar. 31, 2019		1,000,000
Ending balance at Mar. 31, 2019	$ 5,761.9	$ 0	3,794.2	1,990.6	(22.9)
Balance (in shares) at Dec. 31, 2019	1,000,000	1,000,000
Beginning balance at Dec. 31, 2019	$ 6,081.8	$ 0	4,067.9	2,036.4	(22.5)
Increase (Decrease) in Stockholders' Equity
Net income	107			107
Other comprehensive income	0.2				0.2
Dividends declared on common stock	(99.6)			(99.6)
Contribution of capital by parent	$ 80		80
Balance (in shares) at Mar. 31, 2020	1,000,000	1,000,000
Ending balance at Mar. 31, 2020	$ 6,168.6	$ 0	$ 4,147.9	2,043	$ (22.3)
Increase (Decrease) in Stockholders' Equity
Adoption of ASC Topic 326	$ (0.8)			$ (0.8)

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating revenues
Electric, non-affiliates	$ 925.6	$ 958.6
Electric, affiliates	109.6	120.1
Natural gas	206.1	264
Other	8.9	7.8
Total operating revenues	1,250.2	1,350.5
Operating expenses
Electric fuel and purchased power	363.6	391.9
Cost of natural gas sold and transported	125.5	174.4
Cost of sales — other	5.6	5.2
Operating and maintenance expenses	295.7	311.9
Conservation program expenses	31.4	32.5
Depreciation and amortization	202.1	197.7
Taxes (other than income taxes)	68.9	69.6
Total operating expenses	1,092.8	1,183.2
Operating income	157.4	167.3
Other (expense) income, net	(5.4)	1.5
Allowance for funds used during construction — equity	7	5.1
Interest charges and financing costs
Interest charges — includes other financing costs of $1.9 and $1.8, respectively	60.7	57.2
Allowance for funds used during construction — debt	(3.1)	(2.5)
Total interest charges and financing costs	57.6	54.7
Income before income taxes	101.4	119.2
Income tax (benefit) expense	(5.6)	6
Net income	$ 107	$ 113.2

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest charges and financing costs
Other financing costs	$ 1.9	$ 1.8

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Comprehensive income:
Net income	$ 107	$ 113.2
Derivative instruments:
Reclassification of losses to net income, net of tax of $0.1	0.2	0.2
Total other comprehensive income	0.2	0.2
Total comprehensive income	$ 107.2	$ 113.4

CONSOLIDATED STATEMENTS OF CO_2

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

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net income	$ 107	$ 113.2
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	203.9	199
Nuclear fuel amortization	32.5	30.5
Deferred income taxes	(14.9)	(14.6)
Amortization of investment tax credits	(0.3)	(0.3)
Allowance for equity funds used during construction	(7)	(5.1)
Net realized and unrealized hedging and derivative transactions	8.9	6.4
Changes in operating assets and liabilities:
Accounts receivable	8.4	(39)
Accrued unbilled revenues	51.7	49.2
Inventories	20	52.8
Other current assets	(14.7)	(30.2)
Accounts payable	(43)	(48.2)
Net regulatory assets and liabilities	32.8	54.7
Other current liabilities	(3.8)	18
Pension and other employee benefit obligations	(48)	(46.6)
Other, net	6.9	(9.1)
Net cash provided by operating activities	340.4	330.7
Investing activities
Utility capital/construction expenditures	(274.3)	(197.3)
Purchases of investment securities	(835)	(304.7)
Proceeds from the sale of investment securities	829.9	299.6
Investments in utility money pool arrangement	(305)	(38)
Repayments from utility money pool arrangement	257	0
Other, net	1.6	(0.3)
Net cash used in investing activities	(325.8)	(240.7)
Financing activities
Repayments of short-term borrowings, net	(30)	(150)
Borrowings under utility money pool arrangement	118	31
Repayments under utility money pool arrangement	(118)	(31)
Proceeds from issuance of long-term debt	0	0
Repayments of Long-term Debt		0	$ 0
Capital contributions from parent	114	134.9
Dividends paid to parent	(94.3)	(82.8)
Proceeds from (Payments for) Other Financing Activities	(3.4)	0
Net cash used in financing activities	(13.7)	(97.9)
Net change in cash, cash equivalents and restricted cash	0.9	(7.9)
Cash, cash equivalents and restricted cash at beginning of period	126.3	50
Cash, cash equivalents and restricted cash at end of period	127.2	42.1
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(74.7)	(68.2)
Cash paid for income taxes, net	(5.5)	(22)
Supplemental disclosure of non-cash investing and financing transactions:
Accrued property, plant and equipment additions	66.6	110.8
Inventory transfers to plant, property and equipment	4	4.4
Operating lease right-of-use assets	0	444.2
Allowance for equity funds used during construction	$ 7	$ 5.1

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 127,200	$ 126,300
Accounts receivable, net	351,200	359,800
Accounts receivable from affiliates	9,800	43,800
Investments in utility money pool arrangement	48,000	0
Accrued unbilled revenues	197,900	250,700
Inventories	280,700	304,800
Regulatory assets	342,700	320,100
Derivative instruments	22,300	32,500
Prepayments and other	51,000	31,500
Total current assets	1,430,800	1,469,500
Property, plant and equipment	14,290,100	14,244,000
Other assets
Nuclear decommissioning fund and other investments	2,196,200	2,495,200
Regulatory assets	1,343,500	1,125,000
Derivative instruments	25,300	9,200
Operating lease right-of-use assets	544,700	563,800
Other	7,200	9,700
Total other assets	4,116,900	4,202,900
Total assets	19,837,800	19,916,400
Current liabilities
Current portion of long-term debt	300,000	300,000
Short-term debt	0	30,000
Accounts payable	329,900	388,000
Accounts payable to affiliates	65,300	76,000
Regulatory liabilities	144,600	141,000
Taxes accrued	292,000	232,100
Accrued interest	53,000	72,200
Dividends payable to parent	99,600	94,300
Derivative instruments	26,400	25,000
Customer deposits	38,400	46,400
Operating Lease, Liability, Current	81,100	79,900
Other	152,400	154,900
Total current liabilities	1,582,700	1,639,800
Deferred credits and other liabilities
Deferred Income Tax Liabilities, Net	1,687,500	1,779,100
Deferred investment tax credits	19,300	19,700
Regulatory liabilities	1,946,600	1,937,100
Asset retirement obligations	2,308,300	2,280,300
Derivative instruments	122,900	110,200
Pension and employee benefit obligations	187,700	235,900
Operating lease liabilities	505,000	525,700
Other	86,700	85,500
Total deferred credits and other liabilities	6,864,000	6,973,500
Commitments and Contingencies
Capitalization
Long-term debt	5,222,500	5,221,300
Common stock — 5,000,000 shares authorized of $0.01 par value; 1,000,000 shares outstanding at March 31, 2020 and Dec. 31, 2019, respectively	0	0
Additional paid in capital	4,147,900	4,067,900
Retained earnings	2,043,000	2,036,400
Accumulated other comprehensive loss	(22,300)	(22,500)
Total common stockholder’s equity	6,168,600	6,081,800
Total liabilities and equity	$ 19,837,800	$ 19,916,400

CONSOLIDATED BALANCE SHEETS (_2

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Capitalization
Common stock, shares authorized (in shares)	5,000,000	5,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares outstanding (in shares)	1,000,000	1,000,000

Management's Opinion

Management's Opinion	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Opinion	In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments necessary to present fairly, in accordance with U.S. GAAP, the financial position of NSP-Minnesota and its subsidiaries as of March 31, 2020 and Dec. 31, 2019 ; the results of its operations, including the components of net income and comprehensive income, and changes in stockholder’s equity for the three months ended March 31, 2020 and 2019 ; and its cash flows for the three months ended March 31, 2020 and 2019 . All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after March 31, 2020 up to the date of issuance of these consolidated financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation. The Dec. 31, 2019 balance sheet information has been derived from the audited 2019 consolidated financial statements included in the NSP-Minnesota 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 NSP-Minnesota 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 NSP-Minnesota’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	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	The significant accounting policies set forth in Note 1 to the consolidated financial statements in the NSP-Minnesota Annual Report on Form 10-K for the year ended Dec. 31, 2019 , appropriately represent, in all material respects, the current status of accounting policies and are incorporated herein by reference.

Accounting Pronouncements

Accounting Pronouncements	3 Months Ended
	Mar. 31, 2020
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Accounting Pronouncements	Recently Adopted Credit Losses — In 2016, the FASB issued Financial Instruments - Credit Losses, Topic 326 (ASC Topic 326), which changes how entities account for losses on receivables and certain other assets. The guidance requires use of a current expected credit loss model, which may result in earlier recognition of credit losses than under previous accounting standards. NSP-Minnesota implemented the guidance using a modified-retrospective approach, recognizing a cumulative effect charge of $0.8 million

Selected Balance Sheet Data

Selected Balance Sheet Data	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 375.0 $ 382.8 Less allowance for bad debts (23.8 ) (23.0 ) Accounts receivable, net $ 351.2 $ 359.8 (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 177.8 $ 175.6 Fuel 96.1 103.2 Natural gas 6.8 26.0 Total Inventories $ 280.7 $ 304.8 (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Property, plant and equipment Electric plant $ 18,548.7 $ 18,519.5 Natural gas plant 1,578.0 1,562.9 Common and other property 903.9 886.7 Construction work in progress 980.5 846.3 Total property, plant and equipment 22,011.1 21,815.4 Less accumulated depreciation (8,065.8 ) (7,945.3 ) Nuclear fuel 2,913.2 2,909.8 Less accumulated amortization (2,568.4 ) (2,535.9 ) Property, plant and equipment, net $ 14,290.1 $ 14,244.0

Borrowings and Other Financing

Borrowings and Other Financing Instruments	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Borrowings and Other Financing Instruments	4. Borrowings and Other Financing Instruments Short-Term Borrowings NSP-Minnesota 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 NSP-Minnesota were as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end — — Average amount outstanding 10 32 Maximum amount outstanding 116 250 Weighted average interest rate, computed on a daily basis 1.58 % 2.05 % Weighted average interest rate at period end N/A N/A Commercial Paper — Commercial paper outstanding for NSP-Minnesota was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 500 $ 500 Amount outstanding at period end — 30 Average amount outstanding 27 71 Maximum amount outstanding 124 317 Weighted average interest rate, computed on a daily basis 1.77 % 2.59 % Weighted average interest rate at period end N/A 2.05 Letters of Credit — NSP-Minnesota uses letters of credit, generally with terms of one year , to provide financial guarantees for certain operating obligations. At March 31, 2020 and Dec. 31, 2019 , there were $10 million of letters of credit outstanding under the credit facility. 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, NSP-Minnesota 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 amount exceeding available capacity under this credit facility. The line of credit provides short-term financing in the form of notes payable to banks, letters of credit and back-up support for commercial paper borrowings. NSP-Minnesota has the right to request an extension of the revolving credit facility termination date for two additional one year periods. All extension requests are subject to majority bank group approval. At March 31, 2020 , NSP-Minnesota had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 500 $ 10 $ 490 (a) This credit facility expires in June 2024 . (b) Includes outstanding commercial paper and letters of credit. All credit facility bank borrowings, outstanding letters of credit and outstanding commercial paper reduce the available capacity under the credit facility. NSP-Minnesota had no direct advances on the credit facility outstanding at March 31, 2020 and Dec. 31, 2019 . Bilateral Credit Agreement — In March 2019, NSP-Minnesota entered into a one year uncommitted bilateral credit agreement. This facility is limited in use to support letters of credit. In March 2020, NSP-Minnesota renewed its bilateral credit agreement for an additional one-year term. As of March 31, 2020 , NSP-Minnesota’s outstanding letters of credit under the Bilateral Credit Agreement were as follows: (Millions of Dollars) Limit Amount Outstanding Available NSP-Minnesota $ 75 $ 26 $ 49

Revenues

Revenues	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenues	evenue is classified by the type of goods/services rendered and market/customer type. NSP-Minnesota’s operating revenues consists of the following: Three Months Ended March 31, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 300.1 $ 113.5 $ 7.4 $ 421.0 Commercial and industrial 444.7 82.1 — 526.8 Other 7.9 — 1.5 9.4 Total retail 752.7 195.6 8.9 957.2 Wholesale 45.4 — — 45.4 Transmission 55.9 — — 55.9 Interchange 109.6 — — 109.6 Other 1.9 1.2 — 3.1 Total revenue from contracts with customers 965.5 196.8 8.9 1,171.2 Alternative revenue and other 69.7 9.3 — 79.0 Total revenues $ 1,035.2 $ 206.1 $ 8.9 $ 1,250.2 Three Months Ended March 31, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 326.9 $ 149.6 $ 6.9 $ 483.4 Commercial and industrial 467.5 108.8 — 576.3 Other 8.3 — 0.9 9.2 Total retail 802.7 258.4 7.8 1,068.9 Wholesale 46.9 — — 46.9 Transmission 60.4 — — 60.4 Interchange 120.1 — — 120.1 Other 4.8 1.0 — 5.8 Total revenue from contracts with customers 1,034.9 259.4 7.8 1,302.1 Alternative revenue and other 43.8 4.6 — 48.4 Total revenues $ 1,078.7 $ 264.0 $ 7.8 $ 1,350.5

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes Note 7 to the consolidated financial statements included in NSP-Minnesota’s Annual Report on Form 10-K for the year ended Dec. 31, 2019 represents, in all material respects, the current status of other income tax matters except to the extent noted below, and are incorporated herein by reference. The following table reconciles the difference between the statutory rate and the ETR: Three Months Ended March 31 2020 2019 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 7.1 7.1 Increases (decreases) in tax from: Wind PTCs (24.8 ) (14.4 ) Plant regulatory differences (a) (8.3 ) (8.2 ) Other tax credits, net of NOL & tax credit allowances (1.5 ) (1.3 ) Other (net) 1.0 0.8 Effective income tax rate (5.5 )% 5.0 % (a) Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reduction. Federal Audits — NSP-Minnesota is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows: Tax Years Expiration 2009 - 2013 September 2020 2014 - 2016 June 2021 In 2015, the IRS commenced an examination of tax years 2012 and 2013. In 2017, the IRS concluded the audit of tax years 2012 and 2013 and proposed an adjustment that would impact Xcel Energy’s NOL and ETR. Xcel Energy filed a protest with the IRS. As of March 31, 2020 , the case has been forwarded to the Office of Appeals and Xcel Energy has recognized its best estimate of income tax expense that will result from a final resolution of this issue; however, the outcome and timing of a resolution is unknown. In 2018, the IRS began an audit of tax years 2014 - 2016. As of March 31, 2020 , no adjustments have been proposed. State Audits — NSP-Minnesota is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of March 31, 2020 , NSP-Minnesota’s earliest open tax year subject to examination by state taxing authorities under applicable statutes of limitations is 2009. There are currently no state income tax audits in progress. Unrecognized Benefits — Unrecognized tax benefit balance includes permanent tax positions, which if recognized would affect the annual ETR. In addition, the unrecognized tax benefit balance includes temporary tax positions for which ultimate deductibility is highly certain, but for which there is uncertainty about the timing of such deductibility. A change in the period of deductibility would not affect the ETR but would accelerate the payment to the taxing authority to an earlier period. Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 15.5 $ 14.8 Unrecognized tax benefit — Temporary tax positions 4.8 4.9 Total unrecognized tax benefit $ 20.3 $ 19.7 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (17.5 ) $ (16.3 ) Net deferred tax liability associated with the unrecognized tax benefit amounts and related NOLs and tax credits carryforwards were $12.6 million and $11.3 million at March 31, 2020 and Dec. 31, 2019 , respectively. As the IRS Appeals and federal audit progress and state audits resume, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $13.7 million in the next 12 months. Payable for interest related to unrecognized tax benefits is partially offset by the interest benefit associated with NOL and tax credit carryforwards. Interest payable related to unrecognized tax benefits: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Payable for interest related to unrecognized tax benefits at beginning of period $ (1.6 ) $ (1.2 ) Interest expense related to unrecognized tax benefits (0.1 ) (0.4 ) Payable for interest related to unrecognized tax benefits at end of period $ (1.7 ) $ (1.6 ) No amounts were accrued for penalties related to unrecognized tax benefits as of March 31, 2020 or Dec. 31, 2019 .

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	Fair Value Measurements Accounting guidance for fair value measurements and disclosures provides a single definition of fair value and requires disclosures about assets and liabilities measured at fair value. A hierarchical framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value is established by this guidance. • Level 1 — Quoted prices are available in active markets for identical assets or liabilities as of the reporting date. The types of assets and liabilities included in Level 1 are highly liquid and actively traded instruments with quoted prices; • Level 2 — Pricing inputs are other than quoted prices in active markets, but are either directly or indirectly observable as of the reporting date. The types of assets and liabilities included in Level 2 are typically either comparable to actively traded securities or contracts, or priced with models using highly observable inputs; and • Level 3 — Significant inputs to pricing have little or no observability as of the reporting date. The types of assets and liabilities included in Level 3 are those valued with models requiring significant management judgment or estimation. Specific valuation methods include: Cash equivalents — The fair values of cash equivalents are generally based on cost plus accrued interest; money market funds are measured using quoted NAV. Investments in equity securities and other funds — Equity securities are valued using quoted prices in active markets. The fair values for commingled funds are measured using NAVs. The investments in commingled funds may be redeemed for NAV with proper notice. Private equity commingled fund investments require approval of the fund for any unscheduled redemption, and such redemptions may be approved or denied by the fund at its sole discretion. Unscheduled distributions from real estate commingled funds investments may be redeemed with proper notice, however, may be delayed or discounted as a result of fund illiquidity. Investments in debt securities — Fair values for debt securities are determined by a third party pricing service using recent trades and observable spreads from benchmark interest rates for similar securities. 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. Electric commodity derivatives held by NSP-Minnesota include transmission congestion instruments, generally referred to as FTRs. FTRs purchased from a RTO are financial instruments that entitle or obligate the holder to monthly revenues or charges based on transmission congestion across a given transmission path. The value of an FTR is derived from, and designed to offset, the cost of transmission congestion. In addition to overall transmission load, congestion is also influenced by the operating schedules of power plants and the consumption of electricity pertinent to a given transmission path. Unplanned plant outages, scheduled plant maintenance, changes in the relative costs of fuels used in generation, weather and overall changes in demand for electricity can each impact the operating schedules of the power plants on the transmission grid and the value of an FTR. If forecasted costs of electric transmission congestion increase or decrease for a given FTR path, the value of that particular FTR instrument will likewise increase or decrease. Given the limited observability of certain inputs to the value of FTRs between auction processes, including expected plant operating schedules and retail and wholesale demand, fair value measurements for FTRs have been assigned a Level 3. Non-trading monthly FTR settlements are included in fuel and purchased energy cost recovery mechanisms, and therefore changes in the fair value of the yet to be settled portions of most FTRs are deferred as a regulatory asset or liability. Given this regulatory treatment and the limited magnitude of NSP-Minnesota’s FTRs relative to its electric utility operations, the numerous unobservable quantitative inputs pertinent to the value of FTRs are immaterial to the consolidated financial statements of NSP-Minnesota. Non-Derivative Fair Value Measurements The Nuclear Regulatory Commission requires NSP-Minnesota to maintain a portfolio of investments to fund the costs of decommissioning its nuclear generating plants. Assets of the nuclear decommissioning fund are legally restricted for the purpose of decommissioning these facilities. The fund contains cash equivalents, debt securities, equity securities and other investments. NSP-Minnesota uses the MPUC approved asset allocation for the escrow and investment targets by asset class for both the escrow and qualified trust. NSP-Minnesota recognizes the costs of funding the decommissioning over the lives of the nuclear plants, assuming rate recovery of all costs. Realized and unrealized gains on fund investments over the life of the fund are deferred as an offset of NSP-Minnesota’s regulatory asset for nuclear decommissioning costs. Consequently, any realized and unrealized gains and losses on securities in the nuclear decommissioning fund are deferred as a component of the regulatory asset. Unrealized gains for the nuclear decommissioning fund were $454.0 million and $705.5 million as of March 31, 2020 and Dec. 31, 2019 , respectively, and unrealized losses were $88.0 million and $5.9 million as of March 31, 2020 and Dec. 31, 2019 , respectively. Non-derivative instruments with recurring fair value measurements in the nuclear decommissioning fund: March 31, 2020 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 NAV Total Nuclear decommissioning fund (a) Cash equivalents $ 70.5 $ 70.5 $ — $ — $ — $ 70.5 Commingled funds 755.8 — — — 843.0 843.0 Debt securities 514.4 — 488.2 13.2 — 501.4 Equity securities 435.5 726.2 1.1 — — 727.3 Total $ 1,776.2 $ 796.7 $ 489.3 $ 13.2 $ 843.0 $ 2,142.2 (a) Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $54.0 million of rabbi trust assets and miscellaneous investments. Dec. 31, 2019 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 NAV Total Nuclear decommissioning fund (a) Cash equivalents $ 33.4 $ 33.4 $ — $ — $ — $ 33.4 Commingled funds 732.8 — — — 934.9 934.9 Debt securities 489.2 — 495.2 12.7 — 507.9 Equity securities 484.6 962.0 1.4 — — 963.4 Total $ 1,740.0 $ 995.4 $ 496.6 $ 12.7 $ 934.9 $ 2,439.6 (a) Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $55.6 million of rabbi trust assets and miscellaneous investments. For the three months ended March 31, 2020 and 2019 there were immaterial Level 3 nuclear decommissioning fund investments or transfer of amounts between levels. Contractual maturity dates of debt securities in the nuclear decommissioning fund as of March 31, 2020 : Final Contractual Maturity (Millions of Dollars) Due in 1 Year or Less Due in 1 to 5 Years Due in 5 to 10 Years Due after 10 Years Total Debt securities $ 11.3 $ 81.2 $ 205.0 $ 203.9 $ 501.4 Rabbi Trusts NSP-Minnesota has established a rabbi trust to provide partial funding for future deferred compensation plan distributions. Cost and fair value of assets held in rabbi trusts: March 31, 2020 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 Total Rabbi Trusts (a) Cash equivalents $ 1.2 $ 1.2 $ — $ — $ 1.2 Mutual funds 11.4 11.2 — — 11.2 Total $ 12.6 $ 12.4 $ — $ — $ 12.4 Dec. 31, 2019 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 Total Rabbi Trusts (a) Cash equivalents $ 1.2 $ 1.2 $ — $ — $ 1.2 Mutual funds 11.4 13.1 — — 13.1 Total $ 12.6 $ 14.3 $ — $ — $ 14.3 (a) Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet. Derivative Instruments Fair Value Measurements NSP-Minnesota 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 — NSP-Minnesota enters into various instruments that effectively fix the interest payments on certain floating rate debt obligations or effectively fix the yield or price on a specified benchmark interest rate for an anticipated debt issuance for a specific period. These derivative instruments are generally designated as cash flow hedges for accounting purposes. At March 31, 2020 , accumulated other comprehensive loss related to interest rate derivatives included $0.8 million of net losses expected to be reclassified into earnings during the next 12 months as the related hedged interest rate transactions impact earnings. Wholesale and Commodity Trading Risk — NSP-Minnesota 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. NSP-Minnesota 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 — NSP-Minnesota 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, FTRs, vehicle fuel, and weather derivatives. At March 31, 2020 , NSP-Minnesota had no commodity contracts designated as cash flow hedges. NSP-Minnesota may enter into derivative instruments that mitigate commodity price risk on behalf of electric and natural gas customers, but may not be designated as qualifying hedging transactions. Changes in the fair value of non-trading commodity derivative instruments are recorded in other comprehensive income or deferred as a regulatory asset or liability. The classification as a regulatory asset or liability is based on approved regulatory recovery mechanisms. NSP-Minnesota also 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, options and FTRs: (Amounts in Millions) (a)(b) March 31, 2020 Dec. 31, 2019 MWh of electricity 61.0 79.1 MMBtu of natural gas 98.5 77.8 (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 — NSP-Minnesota continuously monitors the creditworthiness of 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. Impact of credit risk was immaterial to the fair value of unsettled commodity derivatives presented in the consolidated balance sheets. NSP-Minnesota’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. As of March 31, 2020 , seven of NSP-Minnesota’s 10 most significant counterparties for these activities, comprising $49.0 million , or 55% , of this credit exposure, had investment grade credit ratings from S&P Global Ratings, Moody’s Investor Services or Fitch Ratings. Two of the 10 most significant counterparties, comprising $15.5 million , or 17% , of this credit exposure, were not rated by these external agencies, but based on NSP-Minnesota’s internal analysis, had credit quality consistent with investment grade. One of these significant counterparties, comprising $12.2 million or 14% of this credit exposure, had credit quality less than investment grade, based on internal analysis. Eight of these significant counterparties are municipal or cooperative electric entities, RTOs or other utilities. As of March 31, 2020 , NSP-Minnesota had no activity for electric and natural gas commodity derivatives that were recognized in regulatory (assets) and liabilities. The impact of derivative activity for Dec. 31, 2019 , is as follows: Pre-Tax Fair Value (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory (Assets) and Liabilities Three Months Ended March 31, 2019 Other derivative instruments Electric commodity $ — $ 5.3 Natural gas commodity — 0.9 Total $ — $ 6.2 Pre-Tax (Gains) Losses Pre-Tax Gains (Losses) (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory Three Months Ended March 31, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.3 (a) $ — $ — Total 0.3 — — Other derivative instruments Commodity trading — — 3.5 (b) Electric commodity — (1.2 ) (c) — Natural gas commodity — 1.1 (d) (2.0 ) (d) Total — (0.1 ) 1.5 Three Months Ended March 31, 2019 Derivatives designated as cash flow hedges Interest rate 0.3 (a) — — Total 0.3 — — Other derivative instruments Commodity trading — — 0.5 (b) Electric commodity — 0.7 (c) — Natural gas commodity — 0.2 (d) (1.3 ) (d) Total $ — $ 0.9 $ (0.8 ) (a) Amounts 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 are recorded to electric fuel and purchased power. These derivative settlement gains and losses are shared with electric customers through fuel and purchased energy cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, as appropriate. (d) Amounts are recorded to cost of natural gas sold and transported. These derivative settlement gains and losses are shared with natural gas customers through purchased natural gas cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, as appropriate. NSP-Minnesota had no derivative instruments designated as fair value hedges during the three months ended March 31, 2020 and 2019 . Credit Related Contingent Features — Contract provisions for derivative instruments that NSP-Minnesota 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 NSP-Minnesota’s credit ratings are downgraded below its investment grade credit rating by any of the major credit rating agencies, or for cross-default contractual provisions if there was a failure under other financing arrangements related to payment terms or other covenants. At March 31, 2020 and Dec. 31, 2019 , there were $11.4 million and $7.1 million 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 NSP-Minnesota’s ability to fulfill its contractual obligations is reasonably expected to be impaired. NSP-Minnesota had no collateral posted related to adequate assurance clauses in derivative contracts as of March 31, 2020 and Dec. 31, 2019 . Recurring Fair Value Measurements — NSP-Minnesota’s derivative assets and liabilities measured at fair value on a recurring basis: March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative assets Other derivative instruments: Commodity trading $ 3.0 $ 48.0 $ 15.8 $ 66.8 $ (47.6 ) $ 19.2 $ 1.6 $ 39.5 $ 23.6 $ 64.7 $ (42.1 ) $ 22.6 Electric commodity — — 3.4 3.4 (0.3 ) 3.1 — — 8.7 8.7 (0.9 ) 7.8 Natural gas commodity — — — — — — — 2.1 — 2.1 — 2.1 Total current derivative assets $ 3.0 $ 48.0 $ 19.2 $ 70.2 $ (47.9 ) $ 22.3 $ 1.6 $ 41.6 $ 32.3 $ 75.5 $ (43.0 ) $ 32.5 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 9.9 $ 31.2 $ 21.4 $ 62.5 $ (37.3 ) $ 25.2 $ 8.5 $ 29.4 $ 6.0 $ 43.9 $ (34.8 ) $ 9.1 Total noncurrent derivative assets $ 9.9 $ 31.2 $ 21.4 $ 62.5 $ (37.3 ) 25.2 $ 8.5 $ 29.4 $ 6.0 $ 43.9 $ (34.8 ) 9.1 PPAs (b) 0.1 0.1 Noncurrent derivative instruments $ 25.3 $ 9.2 March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative liabilities Other derivative instruments: Commodity trading $ 3.8 $ 42.1 $ 14.1 $ 60.0 $ (47.6 ) $ 12.4 $ 2.2 $ 42.1 $ 15.0 $ 59.3 $ (49.8 ) $ 9.5 Electric commodity — — 0.3 0.3 (0.3 ) — — — 1.0 1.0 (1.0 ) — Natural gas commodity — 0.2 — 0.2 — 0.2 — 1.7 — 1.7 — 1.7 Total current derivative liabilities $ 3.8 $ 42.3 $ 14.4 $ 60.5 $ (47.9 ) 12.6 $ 2.2 $ 43.8 $ 16.0 $ 62.0 $ (50.8 ) 11.2 PPAs (b) 13.8 13.8 Current derivative instruments $ 26.4 $ 25.0 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 2.4 $ 44.1 $ 23.4 $ 69.9 $ (5.7 ) $ 64.2 $ 2.0 $ 32.3 $ 17.0 $ 51.3 $ (3.3 ) $ 48.0 Total noncurrent derivative liabilities $ 2.4 $ 44.1 $ 23.4 $ 69.9 $ (5.7 ) 64.2 $ 2.0 $ 32.3 $ 17.0 $ 51.3 $ (3.3 ) 48.0 PPAs (b) 58.7 62.2 Noncurrent derivative instruments $ 122.9 $ 110.2 (a) NSP-Minnesota nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at March 31, 2020 and Dec. 31, 2019 . At both March 31, 2020 and Dec. 31, 2019 , derivative assets and liabilities include $31.5 million of obligations to return cash collateral. At March 31, 2020 , no derivative assets and liabilities include the rights to reclaim cash collateral and $7.9 million at Dec. 31, 2019 . The counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) During 2006, Xcel Energy qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities. Changes in Level 3 commodity derivatives: Three Months Ended March 31 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ 5.3 $ 14.2 Purchases — — Settlements (11.7 ) (3.4 ) Net transactions recorded during the period: Gains (losses) recognized in earnings (a) 6.2 (18.5 ) Net gains (losses) recognized as regulatory assets and liabilities 3.0 (2.4 ) Balance at March 31 $ 2.8 $ (10.1 ) (a) These amounts relate to commodity derivatives held at the end of the period. NSP-Minnesota recognizes transfers between levels as of the beginning of each period. There were no transfers of amounts between levels for derivative instruments for the three months ended March 31, 2020 and 2019 Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: March 31, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Amount Fair Value Carrying Fair Value Long-term debt, including current portion $ 5,522.5 $ 6,264.9 $ 5,521.3 $ 6,296.5 Fair value of NSP-Minnesota’s long-term debt is estimated based on recent trades and observable spreads from benchmark interest rates for similar securities. Fair value estimates are based on information available to management as of March 31, 2020 and Dec. 31, 2019 , and given the observability of the inputs, fair values presented for long-term debt were assigned as Level 2.

Benefit Plans and Other Postret

Benefit Plans and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Components of Net Periodic Benefit Cost Three Months Ended March 31 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Care Benefits Service cost $ 6.7 $ 6.4 $ — $ — Interest cost (a) 7.8 9.3 0.6 0.8 Expected return on plan assets (a) (13.7 ) (13.6 ) — — Amortization of prior service credit (a) — — (0.7 ) (0.8 ) Amortization of net loss (a) 8.1 7.5 0.3 0.4 Net periodic benefit cost 8.9 9.6 0.2 0.4 Costs not recognized due to effects of regulation (1.2 ) (1.2 ) — — Net benefit cost recognized for financial reporting $ 7.7 $ 8.4 $ 0.2 $ 0.4 (a) The components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset. In January 2020, contributions of $150.0 million were made across four of Xcel Energy’s pension plans, of which $44.0 million was attributable to NSP-Minnesota. Xcel Energy does not expect additional pension contributions during 2020.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Legal NSP-Minnesota 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 NSP-Minnesota’s financial statements. Unless otherwise required by GAAP, legal fees are expensed as incurred. Rate Matters MEC Transactions — In November 2018, NSP-Minnesota reached an agreement with Southern Power Company (a subsidiary of Southern Company) to purchase MEC, a 760 MW natural gas combined cycle facility, for approximately $650 million . In September 2019, the MPUC denied NSP-Minnesota's request to purchase MEC as a rate base asset. In January 2020, the MPUC approved Xcel Energy’s plan to acquire MEC as a non-regulated investment and step into the existing PPAs with NSP-Minnesota. A newly formed non-regulated subsidiary of Xcel Energy completed the transaction to purchase MEC in January 2020. In April 2020, Xcel Energy reached agreement to sell MEC to Southwest Generation for $680 million , subject to working capital adjustments. Proceeds from the sale will primarily be used to reduce Xcel Energy’s overall financing needs. The transaction is not anticipated to have a material impact on long-term earnings per share and is expected to close in the third quarter of 2020. The sale will result in a gain, which Xcel Energy plans to use to fund its corporate giving efforts, including support related to COVID-19 recovery. Sherco — In NSP-Minnesota’s 2013 fuel reconciliation filing, the MPUC made recovery of replacement power costs associated with the 2011 incident at its Sherco Unit 3 plant provisional and subject to further review following conclusion of litigation commenced by NSP-Minnesota, SMMPA (Co-owner of Sherco Unit 3) and insurance companies against GE. In 2018, NSP-Minnesota and SMMPA reached a settlement with GE. NSP-Minnesota notified the MPUC of its proposal to refund the GE settlement proceeds back to customers through the FCA. The insurance providers continued their litigation against GE and the case went to trial. In 2018, GE prevailed in the lawsuit with the insurance companies, however, the jury found comparable fault, finding that GE was 52% and NSP-Minnesota was 48% at fault. At that point in the litigation, NSP-Minnesota was no longer involved in the case and was not present to make arguments about its role in the event. The specific issue leading to the fault apportionment was also not before the jury and not relevant to the outcome of the trial. In January 2019, the DOC recommended that NSP-Minnesota refund $20 million of previously recovered purchased power costs to its customers, based on the jury’s apportionment of fault. The OAG recommended the MPUC withhold any decision until the underlying litigation by the insurance providers (currently under appeal) is concluded. The DOC subsequently filed comments agreeing with the OAG’s recommendation to withhold a decision pending the outcome of any appeals. NSP-Minnesota filed reply comments arguing that the DOC recommendations are without merit and that it acted prudently in operating the plant and its settlement with GE was reasonable. In March 2019, MPUC approved NSP-Minnesota’s proposal to refund the GE settlement proceeds back to customers through the FCA. It also decided to withhold any decision as to NSP-Minnesota’s prudence in connection with the incident at Sherco Unit 3 until after conclusion of the pending litigation between GE and NSP-Minnesota’s insurers. The lower court’s decision was affirmed on appeal. In March 2020, NSP-Minnesota’s insurers filed a petition seeking additional review by the Minnesota Supreme Court, which remains pending. MISO ROE Complaints — In November 2013 and February 2015, customers filed complaints against MISO TOs including NSP-Minnesota and NSP-Wisconsin. The first complaint argued for a reduction in the base ROE in MISO transmission formula rates from 12.38% to 9.15% , and removal of ROE adders (including those for RTO membership). The second complaint sought to reduce base ROE from 12.38% to 8.67% . In September 2016, the FERC issued an order granting a 10.32% base ROE ( 10.82% with the RTO adder) effective for the first complaint period of Nov. 12, 2013 to Feb. 11, 2015 and subsequent to the date of the order. The D.C. Circuit subsequently vacated and remanded FERC Opinion No. 531, which had established the ROE methodology on which the September 2016 FERC order was based. On March 21, 2019, FERC announced a NOI seeking public comments on whether, and if so how, to revise ROE policies in light of the D.C. Circuit Court decision. FERC also initiated a NOI on whether to revise its policies on incentives for electric transmission investments, including the RTO membership incentive. In November 2019, the FERC issued an order adopting a new ROE methodology and settling the MISO base ROE at 9.88% ( 10.38% with the RTO adder), effective Sept. 28, 2016 and for the Nov. 12, 2013 to Feb. 11, 2015 refund period. The FERC also dismissed the second complaint. In December 2019, MISO TOs filed a request for rehearing. Customers also filed requests for rehearing claiming, among other points, that the FERC erred by dismissing the second complaint without refunds. FERC accepted the requests for rehearing in January 2020, however, it is uncertain when the FERC will act on the requests or any other pending matters related to the 2019 NOIs . NSP-Minnesota has recognized a liability for its best estimate of final refunds to customers. In March 2020, the FERC issued a Notice of Proposed Rulemaking regarding changes to its policies for transmission incentives, including a proposal to increase the RTO participation adder from 50 to 100 basis points and to make the adder available regardless of whether a utility’s ongoing participation in the RTO is voluntary or required by legislation or a regulator. It is uncertain if or when this change will be adopted and implemented as a final order. Environmental MGP, Landfill and Disposal Sites NSP-Minnesota is currently investigating, remediating or performing post-closure actions at six MGP, landfill or other disposal sites across its service territories. NSP-Minnesota 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 — NSP-Minnesota’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, NSP-Minnesota has three regulated ash units in operation. NSP-Minnesota is conducting groundwater sampling and, where appropriate, implementing assessment of corrective measures at certain CCR landfills and surface impoundments. In 2019, groundwater monitoring consistent with the CCR Rule was conducted. No results above the groundwater protection standards in the rule were identified. Until NSP-Minnesota completes its assessment, it is uncertain what impact, if any, there will be on the operations, financial condition or cash flows. In August 2018, the D.C. Circuit ruled that the EPA cannot allow utilities to continue to use unlined impoundments (including clay lined impoundments) for the storage or disposal of coal ash. In November 2019, the EPA proposed rules in response to this decision. If finalized in their current form, these rules would require NSP-Minnesota to expedite closure plans for one impoundment at an estimated cost of $4 million and the construction of a new impoundment at the cost of $8 million . In 2019, NSP-Minnesota initiated the construction of this new impoundment, an ash pond, expected to be in service in 2020. Upon placing the new ash pond in service, the existing ash pond will be taken out of service, and closure activities as prescribed by the CCR Rule and the facility’s National Pollutant Discharge Elimination System permit will be initiated. Closure costs for existing impoundments are included in the calculation of the asset retirement obligation liability. VIEs Under certain PPAs, NSP-Minnesota purchases power from IPPs for which NSP-Minnesota is required to reimburse fuel costs, or to participate in tolling arrangements under which NSP-Minnesota procures the natural gas required to produce the energy that it purchases. These specific PPAs create a variable interest in the IPP. NSP-Minnesota had approximately 1,347 MW of capacity under long-term PPAs at March 31, 2020 and Dec. 31, 2019 with entities that have been determined to be VIEs. NSP-Minnesota concluded that these entities are not required to be consolidated in its consolidated financial statements because it does not have the power to direct the activities that most significantly impact the entities’ economic performance. Agreements have expiration dates through 2039 .

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Other Comprehensive Income (Loss)	10. Other Comprehensive Income (Loss) Changes in accumulated other comprehensive income (loss), net of tax, for the three months ended March 31, 2020 and 2019 : Three Months Ended March 31, 2020 (Millions of Dollars) Gains and Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (19.4 ) $ (3.1 ) $ (22.5 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.2 — 0.2 Net current period other comprehensive income 0.2 — 0.2 Accumulated other comprehensive loss at March 31 $ (19.2 ) $ (3.1 ) $ (22.3 ) (a) Included in interest charges. Three Months Ended March 31, 2019 (Millions of Dollars) Gains and Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (20.2 ) $ (2.9 ) $ (23.1 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.2 — 0.2 Net current period other comprehensive income 0.2 — 0.2 Accumulated other comprehensive loss at March 31 $ (20.0 ) $ (2.9 ) $ (22.9 ) (a) Included in interest charges.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Segment Information	NSP-Minnesota 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. NSP-Minnesota has the following reportable segments: • Regulated Electric — The regulated electric utility segment generates electricity which is transmitted and distributed in Minnesota, North Dakota and South Dakota. In addition, this segment includes sales for resale and provides wholesale transmission service to various entities in the United States. The regulated electric utility segment also includes NSP‑Minnesota’s wholesale commodity and trading operations; and • Regulated Natural Gas — The regulated natural gas utility segment transports, stores and distributes natural gas in portions of Minnesota and North Dakota. NSP-Minnesota presents Other, which includes operating segments, with revenues below the necessary quantitative thresholds. Those operating segments primarily include appliance repair services, non-utility real estate activities and revenues associated with processing solid waste into refuse‑derived fuel. Asset and capital expenditure information is not provided for NSP-Minnesota’s reportable segments. As an integrated electric and natural gas utility, NSP‑Minnesota operates significant assets that are not dedicated to a specific business segment. 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. Certain costs, such as common depreciation, common O&M expenses and interest expense are allocated based on cost causation allocators across each segment. In addition, a general allocator is used for certain general and administrative expenses, including office supplies, rent, property insurance and general advertising. NSP-Minnesota’s segment information for the three months ended March 31 : (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues (a) $ 1,035.2 $ 1,078.7 Intersegment revenues 0.1 0.1 Total revenue 1,035.3 1,078.8 Net income 86.0 82.9 Regulated Natural Gas Operating revenues (b) $ 206.1 $ 264.0 Intersegment revenues 0.2 0.3 Total revenue 206.3 264.3 Net income 23.3 28.7 All Other Operating revenues $ 8.9 $ 7.8 Net (loss) income (2.3 ) 1.6 Consolidated Total Operating revenues (a)(b) $ 1,250.5 $ 1,350.9 Reconciling eliminations (0.3 ) (0.4 ) Total revenues $ 1,250.2 $ 1,350.5 Net income 107.0 113.2 (a) Operating revenues include $109.6 million and $120.1 million of affiliate electric revenue for the three months ended March 31, 2020 and 2019 . (b) Operating revenues includes an immaterial amount of affiliate gas revenue for the three months ended March 31, 2020 and 2019 .

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Accounts receivable, net Accounts receivable $ 375.0 $ 382.8 Less allowance for bad debts (23.8 ) (23.0 ) Accounts receivable, net $ 351.2 $ 359.8
Inventories	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Inventories Materials and supplies $ 177.8 $ 175.6 Fuel 96.1 103.2 Natural gas 6.8 26.0 Total Inventories $ 280.7 $ 304.8
Property, plant and equipment, net	(Millions of Dollars) March 31, 2020 Dec. 31, 2019 Property, plant and equipment Electric plant $ 18,548.7 $ 18,519.5 Natural gas plant 1,578.0 1,562.9 Common and other property 903.9 886.7 Construction work in progress 980.5 846.3 Total property, plant and equipment 22,011.1 21,815.4 Less accumulated depreciation (8,065.8 ) (7,945.3 ) Nuclear fuel 2,913.2 2,909.8 Less accumulated amortization (2,568.4 ) (2,535.9 ) Property, plant and equipment, net $ 14,290.1 $ 14,244.0

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	At March 31, 2020 , NSP-Minnesota had the following committed revolving credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 500 $ 10 $ 490 (a) This credit facility expires in June 2024 . (b) Includes outstanding commercial paper and letters of credit.
Money Pool
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Money pool borrowings for NSP-Minnesota were as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 250 $ 250 Amount outstanding at period end — — Average amount outstanding 10 32 Maximum amount outstanding 116 250 Weighted average interest rate, computed on a daily basis 1.58 % 2.05 % Weighted average interest rate at period end N/A N/A
Commercial Paper
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Commercial paper outstanding for NSP-Minnesota was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2020 Year Ended Dec. 31, 2019 Borrowing limit $ 500 $ 500 Amount outstanding at period end — 30 Average amount outstanding 27 71 Maximum amount outstanding 124 317 Weighted average interest rate, computed on a daily basis 1.77 % 2.59 % Weighted average interest rate at period end N/A 2.05
Bilateral Credit Agreement | Letter of Credit
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	As of March 31, 2020 , NSP-Minnesota’s outstanding letters of credit under the Bilateral Credit Agreement were as follows: (Millions of Dollars) Limit Amount Outstanding Available NSP-Minnesota $ 75 $ 26 $ 49

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	NSP-Minnesota’s operating revenues consists of the following: Three Months Ended March 31, 2020 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 300.1 $ 113.5 $ 7.4 $ 421.0 Commercial and industrial 444.7 82.1 — 526.8 Other 7.9 — 1.5 9.4 Total retail 752.7 195.6 8.9 957.2 Wholesale 45.4 — — 45.4 Transmission 55.9 — — 55.9 Interchange 109.6 — — 109.6 Other 1.9 1.2 — 3.1 Total revenue from contracts with customers 965.5 196.8 8.9 1,171.2 Alternative revenue and other 69.7 9.3 — 79.0 Total revenues $ 1,035.2 $ 206.1 $ 8.9 $ 1,250.2 Three Months Ended March 31, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 326.9 $ 149.6 $ 6.9 $ 483.4 Commercial and industrial 467.5 108.8 — 576.3 Other 8.3 — 0.9 9.2 Total retail 802.7 258.4 7.8 1,068.9 Wholesale 46.9 — — 46.9 Transmission 60.4 — — 60.4 Interchange 120.1 — — 120.1 Other 4.8 1.0 — 5.8 Total revenue from contracts with customers 1,034.9 259.4 7.8 1,302.1 Alternative revenue and other 43.8 4.6 — 48.4 Total revenues $ 1,078.7 $ 264.0 $ 7.8 $ 1,350.5

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 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: Three Months Ended March 31 2020 2019 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 7.1 7.1 Increases (decreases) in tax from: Wind PTCs (24.8 ) (14.4 ) Plant regulatory differences (a) (8.3 ) (8.2 ) Other tax credits, net of NOL & tax credit allowances (1.5 ) (1.3 ) Other (net) 1.0 0.8 Effective income tax rate (5.5 )% 5.0 % (a) Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reduction.
Summary of Statute of Limitations Applicable to Open Tax Years [Table Text Block]	Federal Audits — NSP-Minnesota is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows: Tax Years Expiration 2009 - 2013 September 2020 2014 - 2016 June 2021
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits — permanent vs temporary: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Unrecognized tax benefit — Permanent tax positions $ 15.5 $ 14.8 Unrecognized tax benefit — Temporary tax positions 4.8 4.9 Total unrecognized tax benefit $ 20.3 $ 19.7
Tax Benefits Associated with NOL and Tax Credit Carryforwards	Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 NOL and tax credit carryforwards $ (17.5 ) $ (16.3 )
Interest Payable related to Unrecognized Tax Benefits [Table Text Block]	Interest payable related to unrecognized tax benefits: (Millions of Dollars) March 31, 2020 Dec. 31, 2019 Payable for interest related to unrecognized tax benefits at beginning of period $ (1.6 ) $ (1.2 ) Interest expense related to unrecognized tax benefits (0.1 ) (0.4 ) Payable for interest related to unrecognized tax benefits at end of period $ (1.7 ) $ (1.6 )

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Cost and Fair Value of Nuclear Decommissioning Fund Investments	Dec. 31, 2019 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 NAV Total Nuclear decommissioning fund (a) Cash equivalents $ 33.4 $ 33.4 $ — $ — $ — $ 33.4 Commingled funds 732.8 — — — 934.9 934.9 Debt securities 489.2 — 495.2 12.7 — 507.9 Equity securities 484.6 962.0 1.4 — — 963.4 Total $ 1,740.0 $ 995.4 $ 496.6 $ 12.7 $ 934.9 $ 2,439.6 (a) Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $55.6 million of rabbi trust assets and miscellaneous investments. Non-derivative instruments with recurring fair value measurements in the nuclear decommissioning fund: March 31, 2020 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 NAV Total Nuclear decommissioning fund (a) Cash equivalents $ 70.5 $ 70.5 $ — $ — $ — $ 70.5 Commingled funds 755.8 — — — 843.0 843.0 Debt securities 514.4 — 488.2 13.2 — 501.4 Equity securities 435.5 726.2 1.1 — — 727.3 Total $ 1,776.2 $ 796.7 $ 489.3 $ 13.2 $ 843.0 $ 2,142.2 (a) Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $54.0 million of rabbi trust assets and miscellaneous investments.
Final Contractual Maturity Dates of Debt Securities in the Nuclear Decommissioning Fund by Asset Class	Contractual maturity dates of debt securities in the nuclear decommissioning fund as of March 31, 2020 : Final Contractual Maturity (Millions of Dollars) Due in 1 Year or Less Due in 1 to 5 Years Due in 5 to 10 Years Due after 10 Years Total Debt securities $ 11.3 $ 81.2 $ 205.0 $ 203.9 $ 501.4
Rabbi Trust Securities Amortized Cost and Fair Value Measured on Recurrring Basis [Table Text Block]	Cost and fair value of assets held in rabbi trusts: March 31, 2020 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 Total Rabbi Trusts (a) Cash equivalents $ 1.2 $ 1.2 $ — $ — $ 1.2 Mutual funds 11.4 11.2 — — 11.2 Total $ 12.6 $ 12.4 $ — $ — $ 12.4 Dec. 31, 2019 Fair Value (Millions of Dollars) Cost Level 1 Level 2 Level 3 Total Rabbi Trusts (a) Cash equivalents $ 1.2 $ 1.2 $ — $ — $ 1.2 Mutual funds 11.4 13.1 — — 13.1 Total $ 12.6 $ 14.3 $ — $ — $ 14.3 (a) Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet.
Gross Notional Amounts of Commodity Forwards, Options, and FTRs	Gross notional amounts of commodity forwards, options and FTRs: (Amounts in Millions) (a)(b) March 31, 2020 Dec. 31, 2019 MWh of electricity 61.0 79.1 MMBtu of natural gas 98.5 77.8 (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	mpact of derivative activity for Dec. 31, 2019 , is as follows: Pre-Tax Fair Value (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory (Assets) and Liabilities Three Months Ended March 31, 2019 Other derivative instruments Electric commodity $ — $ 5.3 Natural gas commodity — 0.9 Total $ — $ 6.2 Pre-Tax (Gains) Losses Pre-Tax Gains (Losses) (Millions of Dollars) Accumulated Other Comprehensive Loss Regulatory Three Months Ended March 31, 2020 Derivatives designated as cash flow hedges Interest rate $ 0.3 (a) $ — $ — Total 0.3 — — Other derivative instruments Commodity trading — — 3.5 (b) Electric commodity — (1.2 ) (c) — Natural gas commodity — 1.1 (d) (2.0 ) (d) Total — (0.1 ) 1.5 Three Months Ended March 31, 2019 Derivatives designated as cash flow hedges Interest rate 0.3 (a) — — Total 0.3 — — Other derivative instruments Commodity trading — — 0.5 (b) Electric commodity — 0.7 (c) — Natural gas commodity — 0.2 (d) (1.3 ) (d) Total $ — $ 0.9 $ (0.8 ) (a) Amounts 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 are recorded to electric fuel and purchased power. These derivative settlement gains and losses are shared with electric customers through fuel and purchased energy cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, as appropriate. (d) Amounts are recorded to cost of natural gas sold and transported. These derivative settlement gains and losses are shared with natural gas customers through purchased natural gas cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, as appropriate.
Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level	Recurring Fair Value Measurements — NSP-Minnesota’s derivative assets and liabilities measured at fair value on a recurring basis: March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative assets Other derivative instruments: Commodity trading $ 3.0 $ 48.0 $ 15.8 $ 66.8 $ (47.6 ) $ 19.2 $ 1.6 $ 39.5 $ 23.6 $ 64.7 $ (42.1 ) $ 22.6 Electric commodity — — 3.4 3.4 (0.3 ) 3.1 — — 8.7 8.7 (0.9 ) 7.8 Natural gas commodity — — — — — — — 2.1 — 2.1 — 2.1 Total current derivative assets $ 3.0 $ 48.0 $ 19.2 $ 70.2 $ (47.9 ) $ 22.3 $ 1.6 $ 41.6 $ 32.3 $ 75.5 $ (43.0 ) $ 32.5 Noncurrent derivative assets Other derivative instruments: Commodity trading $ 9.9 $ 31.2 $ 21.4 $ 62.5 $ (37.3 ) $ 25.2 $ 8.5 $ 29.4 $ 6.0 $ 43.9 $ (34.8 ) $ 9.1 Total noncurrent derivative assets $ 9.9 $ 31.2 $ 21.4 $ 62.5 $ (37.3 ) 25.2 $ 8.5 $ 29.4 $ 6.0 $ 43.9 $ (34.8 ) 9.1 PPAs (b) 0.1 0.1 Noncurrent derivative instruments $ 25.3 $ 9.2 March 31, 2020 Dec. 31, 2019 Fair Value Fair Value Netting (a) Fair Value Fair Value Netting (a) (Millions of Dollars) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Current derivative liabilities Other derivative instruments: Commodity trading $ 3.8 $ 42.1 $ 14.1 $ 60.0 $ (47.6 ) $ 12.4 $ 2.2 $ 42.1 $ 15.0 $ 59.3 $ (49.8 ) $ 9.5 Electric commodity — — 0.3 0.3 (0.3 ) — — — 1.0 1.0 (1.0 ) — Natural gas commodity — 0.2 — 0.2 — 0.2 — 1.7 — 1.7 — 1.7 Total current derivative liabilities $ 3.8 $ 42.3 $ 14.4 $ 60.5 $ (47.9 ) 12.6 $ 2.2 $ 43.8 $ 16.0 $ 62.0 $ (50.8 ) 11.2 PPAs (b) 13.8 13.8 Current derivative instruments $ 26.4 $ 25.0 Noncurrent derivative liabilities Other derivative instruments: Commodity trading $ 2.4 $ 44.1 $ 23.4 $ 69.9 $ (5.7 ) $ 64.2 $ 2.0 $ 32.3 $ 17.0 $ 51.3 $ (3.3 ) $ 48.0 Total noncurrent derivative liabilities $ 2.4 $ 44.1 $ 23.4 $ 69.9 $ (5.7 ) 64.2 $ 2.0 $ 32.3 $ 17.0 $ 51.3 $ (3.3 ) 48.0 PPAs (b) 58.7 62.2 Noncurrent derivative instruments $ 122.9 $ 110.2 (a) NSP-Minnesota nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at March 31, 2020 and Dec. 31, 2019 . At both March 31, 2020 and Dec. 31, 2019 , derivative assets and liabilities include $31.5 million of obligations to return cash collateral. At March 31, 2020 , no derivative assets and liabilities include the rights to reclaim cash collateral and $7.9 million at Dec. 31, 2019 . The counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) During 2006, Xcel Energy qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.
Changes in Level 3 Commodity Derivatives	Changes in Level 3 commodity derivatives: Three Months Ended March 31 (Millions of Dollars) 2020 2019 Balance at Jan. 1 $ 5.3 $ 14.2 Purchases — — Settlements (11.7 ) (3.4 ) Net transactions recorded during the period: Gains (losses) recognized in earnings (a) 6.2 (18.5 ) Net gains (losses) recognized as regulatory assets and liabilities 3.0 (2.4 ) Balance at March 31 $ 2.8 $ (10.1 ) (a) These 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: March 31, 2020 Dec. 31, 2019 (Millions of Dollars) Carrying Amount Fair Value Carrying Fair Value Long-term debt, including current portion $ 5,522.5 $ 6,264.9 $ 5,521.3 $ 6,296.5

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost (Credit)	Components of Net Periodic Benefit Cost Three Months Ended March 31 2020 2019 2020 2019 (Millions of Dollars) Pension Benefits Postretirement Health Care Benefits Service cost $ 6.7 $ 6.4 $ — $ — Interest cost (a) 7.8 9.3 0.6 0.8 Expected return on plan assets (a) (13.7 ) (13.6 ) — — Amortization of prior service credit (a) — — (0.7 ) (0.8 ) Amortization of net loss (a) 8.1 7.5 0.3 0.4 Net periodic benefit cost 8.9 9.6 0.2 0.4 Costs not recognized due to effects of regulation (1.2 ) (1.2 ) — — Net benefit cost recognized for financial reporting $ 7.7 $ 8.4 $ 0.2 $ 0.4 (a) The components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax	Changes in accumulated other comprehensive income (loss), net of tax, for the three months ended March 31, 2020 and 2019 : Three Months Ended March 31, 2020 (Millions of Dollars) Gains and Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (19.4 ) $ (3.1 ) $ (22.5 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.2 — 0.2 Net current period other comprehensive income 0.2 — 0.2 Accumulated other comprehensive loss at March 31 $ (19.2 ) $ (3.1 ) $ (22.3 ) (a) Included in interest charges. Three Months Ended March 31, 2019 (Millions of Dollars) Gains and Defined Benefit Pension and Postretirement Items Total Accumulated other comprehensive loss at Jan. 1 $ (20.2 ) $ (2.9 ) $ (23.1 ) Losses reclassified from net accumulated other comprehensive loss: Interest rate derivatives (net of taxes of $0.1 and $0, respectively) (a) 0.2 — 0.2 Net current period other comprehensive income 0.2 — 0.2 Accumulated other comprehensive loss at March 31 $ (20.0 ) $ (2.9 ) $ (22.9 ) (a) Included in interest charges.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Results from Operations by Reportable Segment	NSP-Minnesota’s segment information for the three months ended March 31 : (Millions of Dollars) 2020 2019 Regulated Electric Operating revenues (a) $ 1,035.2 $ 1,078.7 Intersegment revenues 0.1 0.1 Total revenue 1,035.3 1,078.8 Net income 86.0 82.9 Regulated Natural Gas Operating revenues (b) $ 206.1 $ 264.0 Intersegment revenues 0.2 0.3 Total revenue 206.3 264.3 Net income 23.3 28.7 All Other Operating revenues $ 8.9 $ 7.8 Net (loss) income (2.3 ) 1.6 Consolidated Total Operating revenues (a)(b) $ 1,250.5 $ 1,350.9 Reconciling eliminations (0.3 ) (0.4 ) Total revenues $ 1,250.2 $ 1,350.5 Net income 107.0 113.2 (a) Operating revenues include $109.6 million and $120.1 million of affiliate electric revenue for the three months ended March 31, 2020 and 2019 . (b) Operating revenues includes an immaterial amount of affiliate gas revenue for the three months ended March 31, 2020 and 2019 .

Accounting Pronouncements (Deta

Accounting Pronouncements (Details) - USD ($) $ in Millions	Jan. 01, 2020	Mar. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit Losses, Topic 326 (ASC Topic 326)		$ 0.8
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit Losses, Topic 326 (ASC Topic 326)	$ 0.8	$ 0.8

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable	$ 375	$ 382.8
Less allowance for bad debts	(23.8)	(23)
Accounts receivable, net	$ 351.2	$ 359.8

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Public Utilities, Inventory [Line Items]
Inventories	$ 280,700	$ 304,800
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	177,800	175,600
Fuel
Public Utilities, Inventory [Line Items]
Inventories	96,100	103,200
Natural Gas
Public Utilities, Inventory [Line Items]
Inventories	$ 6,800	$ 26,000

Property, Plant and Equipment (

Property, Plant and Equipment (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 22,011.1	$ 21,815.4
Accumulated depreciation and amortization	(8,065.8)	(7,945.3)
Property, plant and equipment, net	14,290.1	14,244
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	18,548.7	18,519.5
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,578	1,562.9
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	903.9	886.7
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	980.5	846.3
Nuclear fuel
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,913.2	2,909.8
Accumulated depreciation and amortization	$ (2,568.4)	$ (2,535.9)

Money Pool (Details)

Money Pool (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Amount outstanding at period end	$ 0	$ 30
Money Pool
Short-term Debt [Line Items]
Borrowing limit	250	250
Amount outstanding at period end	0	0
Average amount outstanding	10	32
Maximum amount outstanding	$ 116	$ 250
Weighted average interest rate, computed on a daily basis	1.58%	2.05%

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments Commercial Paper (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Amount outstanding at period end	$ 0	$ 30
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	500	500
Amount outstanding at period end	0	30
Average amount outstanding	27	71
Maximum amount outstanding	$ 124	$ 317
Weighted average interest rate, computed on a daily basis	1.77%	2.59%
Weighted average interest rate at period end		2.05%

Letters of Credit (Details)

Letters of Credit (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 0	$ 30
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 10	$ 10

Credit Facility (Details)

Credit Facility (Details)		3 Months Ended
		Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Line of Credit Facility [Line Items]
Amount outstanding at period end		$ 0	$ 30,000,000
Credit Facility
Line of Credit Facility [Line Items]
Debt Instrument, Term		1 year
Borrowing limit	[1]	$ 500,000,000
Amount outstanding at period end	[2]	$ 10,000,000
Number of extension you can request		2
Available		$ 490,000,000
Direct advances on the credit facility outstanding		0	0
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end		$ 10,000,000	$ 10,000,000
[1]	This credit facility expires in June 2024 .
[2]	Includes outstanding commercial paper and letters of credit.

Bilateral Credit Agreement (Det

Bilateral Credit Agreement (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Amount outstanding at period end	$ 0	$ 30
Letter of Credit
Short-term Debt [Line Items]
Amount outstanding at period end	10	$ 10
Letter of Credit | Bilateral Credit Agreement
Short-term Debt [Line Items]
Borrowing Limit	75
Amount outstanding at period end	26
Available	$ 49

Revenues (Details)

Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,250.2	$ 1,350.5
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	1,035.2	1,078.7
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	206.1	264
All Other | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	8.9	7.8
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,171.2	1,302.1
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	965.5	1,034.9
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	196.8	259.4
Total revenue from contracts with customers | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8.9	7.8
Retail
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	957.2	1,068.9
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	421	483.4
Retail | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	526.8	576.3
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	9.4	9.2
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	752.7	802.7
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	300.1	326.9
Retail | Regulated Electric | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	444.7	467.5
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	7.9	8.3
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	195.6	258.4
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	113.5	149.6
Retail | Regulated Natural Gas | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	82.1	108.8
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Retail | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8.9	7.8
Retail | All Other | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	7.4	6.9
Retail | All Other | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Retail | All Other | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1.5	0.9
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	45.4	46.9
Wholesale | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	45.4	46.9
Wholesale | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Wholesale | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Transmission
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	55.9	60.4
Transmission | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	55.9	60.4
Transmission | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Transmission | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Interchange [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	109.6	120.1
Interchange [Member] | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	109.6	120.1
Interchange [Member] | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Interchange [Member] | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.1	5.8
Other | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1.9	4.8
Other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1.2	1
Other | All Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	79	48.4
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	69.7	43.8
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	9.3	4.6
Alternative revenue and other | All Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 0	$ 0

Income Taxes (Details)

Income Taxes (Details)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Income Tax Examination [Line Items]
Federal statutory rate		21.00%	21.00%
State tax (net of federal tax effect)		7.10%	7.10%
Wind PTCs		(24.80%)	(14.40%)
Plant regulatory differences (a)	[1]	(8.30%)	(8.20%)
Other tax credits, net of NOL & tax credit allowances		(1.50%)	(1.30%)
Other (net)		1.00%	0.80%
Effective income tax rate		(5.50%)	5.00%
[1]	Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method

Income Taxes Federal Audits (De

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

Income Taxes Unrecognized Benef

Income Taxes Unrecognized Benefits (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Uncertainty [Abstract]
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	$ (1,700,000)	$ (1,600,000)	$ (1,200,000)
Interest Expense (Income) related to unrecognized tax benefits	(100,000)	(400,000)
Unrecognized tax benefit — Permanent tax positions	15,500,000	14,800,000
Unrecognized tax benefit — Temporary tax positions	4,800,000	4,900,000
Total unrecognized tax benefit	20,300,000	19,700,000
NOL and tax credit carryforwards	17,500,000	16,300,000
Net Deferred Tax Liability associated with the Unrecognized Tax Benefit Amounts and Related NOLs and Tax Credit Carryforwards	(12,600,000)	(11,300,000)
Decrease in Unrecognized Tax Benefits is Reasonably Possible	13,700,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	$ 0	$ 0

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities Non-Derivative Fair Value Measurements (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020		Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain on Securities	$ 454		$ 705.5
Unrealized Loss on Securities	88		5.9
Nuclear Decommissioning Fund [Abstract]
Miscellaneous investments	54		55.6
Final Contractual Maturity [Abstract]
Due in 1 Year or Less	11.3
Due in 1 to 5 Years	81.2
Due in 5 to 10 Years	205
Due after 10 Years	203.9
Total	501.4
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost
Nuclear Decommissioning Fund [Abstract]
Total	1,776.2	[1]	1,740	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Cash equivalents
Nuclear Decommissioning Fund [Abstract]
Cash equivalents	70.5	[1]	33.4	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Commingled Funds [Member]
Nuclear Decommissioning Fund [Abstract]
Commingled funds	755.8	[1]	732.8	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Debt Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Debt securities	514.4	[1]	489.2	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Cost | Equity Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Equity securities	435.5	[1]	484.6	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value
Nuclear Decommissioning Fund [Abstract]
NAV	843	[1]	934.9	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Cash equivalents
Nuclear Decommissioning Fund [Abstract]
Cash equivalents	70.5	[1]	33.4	[2]
NAV	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Commingled Funds [Member]
Nuclear Decommissioning Fund [Abstract]
Commingled funds	843	[1]	934.9	[2]
NAV	843	[1]	934.9	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Debt Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Debt securities	501.4	[1]	507.9	[2]
NAV	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Equity Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Equity securities	727.3	[1]	963.4	[2]
NAV	0	[1]	0	[2]
Total	2,142.2	[1]	2,439.6	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1
Nuclear Decommissioning Fund [Abstract]
Total	796.7	[1]	995.4	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Cash equivalents
Nuclear Decommissioning Fund [Abstract]
Cash equivalents	70.5	[1]	33.4	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Commingled Funds [Member]
Nuclear Decommissioning Fund [Abstract]
Commingled funds	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Debt Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Debt securities	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Equity Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Equity securities	726.2	[1]	962	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2
Nuclear Decommissioning Fund [Abstract]
Total	489.3	[1]	496.6	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Cash equivalents
Nuclear Decommissioning Fund [Abstract]
Cash equivalents	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Commingled Funds [Member]
Nuclear Decommissioning Fund [Abstract]
Commingled funds	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Debt Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Debt securities	488.2	[1]	495.2	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Equity Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Equity securities	1.1	[1]	1.4	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3
Nuclear Decommissioning Fund [Abstract]
Total	13.2	[1]	12.7	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Cash equivalents
Nuclear Decommissioning Fund [Abstract]
Cash equivalents	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Commingled Funds [Member]
Nuclear Decommissioning Fund [Abstract]
Commingled funds	0	[1]	0	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Debt Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Debt securities	13.2	[1]	12.7	[2]
Nuclear Decommissioning Fund | Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Equity Securities [Member]
Nuclear Decommissioning Fund [Abstract]
Equity securities	$ 0	[1]	$ 0	[2]
[1]	Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $54.0 million of rabbi trust assets and miscellaneous investments.
[2]	Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $55.6 million of rabbi trust assets and miscellaneous investments.

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities Rabbi Trust (Details) - Rabbi Trust [Member] - Fair Value Measured on a Recurring Basis - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	[1]	$ 12.6	$ 12.6
Cost | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[1]	1.2	1.2
Cost | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	[1]	11.4	11.4
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	[1]	12.4	14.3
Fair Value | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[1]	1.2	1.2
Fair Value | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	[1]	11.2	13.1
Fair Value | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	[1]	12.4	14.3
Fair Value | Level 1 | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[1]	1.2	1.2
Fair Value | Level 1 | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	[1]	11.2	13.1
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	[1]	0	0
Fair Value | Level 2 | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[1]	0	0
Fair Value | Level 2 | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	[1]	0	0
Fair Value | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	[1]	0	0
Fair Value | Level 3 | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[1]	0	0
Fair Value | Level 3 | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	[1]	$ 0	$ 0
[1]	Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet.

Interest Rate Derivative (Detai

Interest Rate Derivative (Details) $ in Millions	Mar. 31, 2020USD ($)
Interest Rate Derivatives
Interest Rate Derivatives [Abstract]
Amount or interest rate derivatives expected to be reclassified	$ (0.8)

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Mar. 31, 2020USD ($)MMBTUMWh	Dec. 31, 2019MMBTUMWh
Cash flow hedge commodity
Derivative [Line Items]
Commodity contracts designated as cash flow hedges | $		$ 0
Electric commodity
Gross Notional Amounts of Commodity Forwards, Options and FTRs [Abstract]
Derivative, Nonmonetary Notional amount | MWh	[1],[2]	61	79.1
Natural gas commodity
Gross Notional Amounts of Commodity Forwards, Options and FTRs [Abstract]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	98.5	77.8
[1]	Amounts are not reflective of net positions in the underlying commodities.
[2]	Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities Consideration of Credit Risk and Concentrations (Details) $ in Millions		3 Months Ended
		Mar. 31, 2020USD ($)Counterparty	Mar. 31, 2019USD ($)
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Fair Value Hedges, Net		$ 0	$ 0
Not Designated as Hedging Instrument [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in accumulated other comprehensive loss			0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities			6.2
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss		0	0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		(0.1)	(0.9)
Pre-tax gains (losses) recognized during the period in income		1.5	(0.8)
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in accumulated other comprehensive loss			0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities		0	0.9
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss		0	0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	[1]	(1.1)	(0.2)
Pre-tax gains (losses) recognized during the period in income	[1]	(2)	(1.3)
Not Designated as Hedging Instrument [Member] | Electric Commodity Contract [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in accumulated other comprehensive loss			0
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities		0	5.3
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss		0	0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	[2]	(1.2)	(0.7)
Pre-tax gains (losses) recognized during the period in income		0	0
Not Designated as Hedging Instrument [Member] | Commodity Trading Contract [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss		0	0
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		0	0
Pre-tax gains (losses) recognized during the period in income	[3]	3.5	0.5
Designated as Hedging Instrument [Member] | Cash Flow Hedges
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss		0.3	0.3
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		0	0
Pre-tax gains (losses) recognized during the period in income		0	0
Designated as Hedging Instrument [Member] | Cash Flow Hedges | Interest Rate Contract [Member]
Impact of Derivative Activity on Accumulated Other Comprehensive Loss, Regulatory Assets and Liabilities, and Income [Abstract]
Pre-tax (gains) losses reclassified into income during the period from accumulated other comprehensive loss	[4]	0.3	0.3
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)		0	0
Pre-tax gains (losses) recognized during the period in income		$ 0	$ 0
Credit Concentration Risk
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		10
Credit Concentration Risk | Municipal or Cooperative Entities or Other Utilities [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		8
Credit Concentration Risk | External Credit Rating, Investment Grade [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		7
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties		$ 49
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties		55.00%
Credit Concentration Risk | Internal Investment Grade [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		2
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties		$ 15.5
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties		17.00%
Credit Concentration Risk | External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Number of most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure | Counterparty		1
Wholesale, trading and non trading commodity credit exposure for the most significant counterparties		$ 12.2
Percentage of wholesale, trading and non trading commodity credit exposure for the most significant counterparties		14.00%
[1]	Amounts are recorded to cost of natural gas sold and transported. These derivative settlement gains and losses are shared with natural gas customers through purchased natural gas cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, as appropriate.
[2]	Amounts are recorded to electric fuel and purchased power. These derivative settlement gains and losses are shared with electric customers through fuel and purchased energy cost-recovery mechanisms, and reclassified out of income as regulatory assets or liabilities, 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 recorded to interest charges.

Credit Related Contingent Featu

Credit Related Contingent Features (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Derivative instruments in a gross liability position	$ 11.4	$ 7.1
Collateral posted related to adequate assurance clauses in derivative contracts	$ 0	$ 0

Recurring Fair Value Measuremen

Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Obligation to return cash		$ 31.5		$ 31.5
Right to reclaim cash		0		7.9
Commodity Trading
Changes in Level 3 Commodity Derivatives [Roll Forward]
Balance at beginning of period		5.3	$ 14.2
Purchases		0	0
Settlements		(11.7)	(3.4)
Gains (losses) recognized in earnings	[1]	6.2	(18.5)
Net gains (losses) recognized as regulatory assets and liabilities		3	(2.4)
Balance at end of period		2.8	(10.1)
Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative asset		25.3		9.2
Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability		26.4		25
Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability		122.9		110.2
Fair Value Measured on a Recurring Basis | Level 3
Changes in Level 3 Commodity Derivatives [Roll Forward]
Transfers level 3, net		0	$ 0
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative asset, gross		70.2		75.5
Netting, asset	[2]	(47.9)		(43)
Derivative asset		22.3		32.5
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative asset, gross		3		1.6
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative asset, gross		48		41.6
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative asset, gross		19.2		32.3
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		66.8		64.7
Netting, asset	[2]	(47.6)		(42.1)
Derivative asset		19.2		22.6
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		3.4		8.7
Netting, asset	[2]	(0.3)		(0.9)
Derivative asset		3.1		7.8
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		0		2.1
Netting, asset	[2]	0		0
Derivative asset		0		2.1
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		3		1.6
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 1 | Electric 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 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		48		39.5
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 2 | Electric 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 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		0		2.1
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		15.8		23.6
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Level 3 | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		3.4		8.7
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		62.5		43.9
Netting, asset	[2]	(37.3)		(34.8)
Derivative asset		25.2		9.1
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative asset, gross		9.9		8.5
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative asset, gross		31.2		29.4
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative asset, gross		21.4		6
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		62.5		43.9
Netting, asset	[2]	(37.3)		(34.8)
Derivative asset		25.2		9.1
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		9.9		8.5
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		31.2		29.4
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		21.4		6
Fair Value Measured on a Recurring Basis | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, gross		60.5		62
Netting, liability	[2]	(47.9)		(50.8)
Derivative liability		12.6		11.2
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative liability, gross		3.8		2.2
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative liability, gross		42.3		43.8
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative liability, gross		14.4		16
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative liability, gross		60		59.3
Netting, liability	[2]	(47.6)		(49.8)
Derivative liability		12.4		9.5
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative liability, gross		0.3		1
Netting, liability	[2]	(0.3)		(1)
Derivative liability		0		0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative liability, gross		0.2		1.7
Netting, liability	[2]	0		0
Derivative liability		0.2		1.7
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		3.8		2.2
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 1 | Electric 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 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		42.1		42.1
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 2 | Electric 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 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative liability, gross		0.2		1.7
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		14.1		15
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Level 3 | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative liability, gross		0.3		1
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		69.9		51.3
Netting, liability	[2]	(5.7)		(3.3)
Derivative liability		64.2		48
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative liability, gross		2.4		2
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative liability, gross		44.1		32.3
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative liability, gross		23.4		17
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative liability, gross		69.9		51.3
Netting, liability	[2]	(5.7)		(3.3)
Derivative liability		64.2		48
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		2.4		2
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		44.1		32.3
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		23.4		17
Fair Value, Measurements, Nonrecurring | Other Noncurrent Assets | PPAs
Derivatives, Fair Value [Line Items]
Derivative asset	[3]	0.1		0.1
Fair Value, Measurements, Nonrecurring | Other Current Liabilities | PPAs
Derivatives, Fair Value [Line Items]
Derivative liability	[3]	13.8		13.8
Fair Value, Measurements, Nonrecurring | Other Noncurrent Liabilities | PPAs
Derivatives, Fair Value [Line Items]
Derivative liability	[3]	$ 58.7		$ 62.2
[1]	These amounts relate to commodity derivatives held at the end of the period.
[2]	NSP-Minnesota nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at March 31, 2020 and Dec. 31, 2019 . At both March 31, 2020 and Dec. 31, 2019 , derivative assets and liabilities include $31.5 million of obligations to return cash collateral. At March 31, 2020 , no derivative assets and liabilities include the rights to reclaim cash collateral and $7.9 million at Dec. 31, 2019 . The counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.
[3]	During 2006, Xcel Energy qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.

Fair Value of Long-Term Debt (D

Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying amount	$ 5,522.5	$ 5,521.3
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 6,264.9	$ 6,296.5

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended
		Jan. 31, 2020USD ($)Plan	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost			$ 6.7	$ 6.4
Interest cost	[1]		7.8	9.3
Expected return on plan assets	[1]		(13.7)	(13.6)
Amortization of prior service credit	[1]		0	0
Amortization of net loss	[1]		8.1	7.5
Net periodic benefit cost			8.9	9.6
Costs not recognized due to effects of regulation			(1.2)	(1.2)
Net benefit cost recognized for financial reporting			7.7	8.4
Total contributions to the pension plans during the period		$ 44
Pension Plan [Member] | Xcel Energy Inc.
Components of Net Periodic Benefit Cost [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 [Abstract]
Service cost			0	0
Interest cost	[1]		0.6	0.8
Expected return on plan assets	[1]		0	0
Amortization of prior service credit	[1]		(0.7)	(0.8)
Amortization of net loss	[1]		0.3	0.4
Net periodic benefit cost			0.2	0.4
Costs not recognized due to effects of regulation			0	0
Net benefit cost recognized for financial reporting			$ 0.2	$ 0.4
[1]	The components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Commitments and Contingencies M

Commitments and Contingencies MEC Transactions (Details) - MEC Holdings LLC [Member] - Unregulated Operation [Member] $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)MW
Public Utilities, General Disclosures [Line Items]
Natural Gas Combine Cycle Facility Output | MW		760
Property, Plant and Equipment, Additions		$ 650
Proceeds from Sale of Property, Plant, and Equipment	$ 680

Sherco (Details)

Sherco (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018
General Electric (GE) [Domain]
Rate Matters [Abstract]
Percentage of Fault		52.00%
NSP-Minnesota
Rate Matters [Abstract]
Percentage of Fault		48.00%
Customer refund of previously recovered purchased power costs	$ 20

Commitments and Contingencies_2

Commitments and Contingencies MISO ROE Complaints (Details) - Federal Energy Regulatory Commission (FERC) - FERC Proceeding, MISO ROE Complaint - NSP Minnesota and NSP Wisconsin [Member] [Member]	1 Months Ended		12 Months Ended	39 Months Ended
	Feb. 28, 2015	Nov. 30, 2013	Dec. 31, 2016	Dec. 31, 2019	Mar. 31, 2020
Public Utilities, General Disclosures [Line Items]
Public Utilities, Base Return On Equity Charged To Customers Through Transmission Formula Rates	12.38%	12.38%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Recommended By Third Parties	8.67%	9.15%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Approved			10.32%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, with RTO Adder, Approved			10.82%
Public Utilities, ROE developed with new approach				9.88%
Public Utilities, ROE developed with new approach, with RTO Adder, Approved				10.38%
Minimum [Member]
Public Utilities, General Disclosures [Line Items]
basis points					50
Maximum [Member]
Public Utilities, General Disclosures [Line Items]
basis points					100

Environmental, MGP, Landfill or

Environmental, MGP, Landfill or Disposal Sites (Details)	Mar. 31, 2020
Other MGP, Landfill, or Disposal Sites [Domain]
Site Contingency [Line Items]
Number of identified MGP, landfill, or disposal sites under current investigation and/or remediation	6

Commitments and Contingencies E

Commitments and Contingencies Environmental Requirements - Water and Waste (Details) - Federal Coal Ash Regulation [Domain] $ in Millions	Mar. 31, 2020USD ($)
Site Contingency [Line Items]
Number of sites where regulated ash units will still be in operation at a specified date	3
Number of sites where statistically significant increases over established groundwater standards exist	0
Number of impoundments where closure plans will be expedited	1
Estimated cost of closure of an impoundment	$ 4
Estimated cost of construction of a new impoundment	$ 8

Commitments and Contingencies V

Commitments and Contingencies Variable Interest Entities (Details) - MW	Mar. 31, 2020	Dec. 31, 2019
Independent Power Producing Entities
Variable Interest Entity [Line Items]
Generating capacity under long term purchased power agreements	1,347	1,347

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income at beginning of period	$ 6,081.8
Accumulated other comprehensive (loss) income at end of period	6,168.6
Income Tax Expense (Benefit)	(5.6)		$ 6
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income at beginning of period	(19.4)		(20.2)
Other Comprehensive Income (Loss), Net of Tax	0.2		0.2
Accumulated other comprehensive (loss) income at end of period	(19.2)		(20)
Gains and Losses on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	0		0
Income Tax Expense (Benefit)	0.1		0.1
Reclassification from AOCI, Current Period, Tax	0		0
Gains and Losses on Cash Flow Hedges | Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
(Gains) losses reclassified from net accumulated other comprehensive loss	(0.2)	[1]	(0.2)	[2]
Defined Benefit Pension and Postretirement Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income at beginning of period	(3.1)		(2.9)
Other Comprehensive Income (Loss), Net of Tax	0		0
Accumulated other comprehensive (loss) income at end of period	(3.1)		(2.9)
Defined Benefit Pension and Postretirement Items | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	0		0
Income Tax Expense (Benefit)	0		0
Reclassification from AOCI, Current Period, Tax	0		0
Defined Benefit Pension and Postretirement Items | Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
(Gains) losses reclassified from net accumulated other comprehensive loss	0	[1]	0	[2]
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income at beginning of period	(22.5)		(23.1)
Other Comprehensive Income (Loss), Net of Tax	0.2		0.2
Accumulated other comprehensive (loss) income at end of period	(22.3)		(22.9)
Total | Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
(Gains) losses reclassified from net accumulated other comprehensive loss	$ (0.2)	[1]	$ (0.2)	[2]
[1]	Included in interest charges.
[2]	Included in interest charges.

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Net income		$ 107	$ 113.2
Regulated Operating Revenue, Gas		206.1	264
Unregulated Operating Revenue		8.9	7.8
Regulated and Unregulated Operating Revenue		1,250.2	1,350.5
Affiliate Revenue		109.6	120.1
Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Revenues Including Intersegment Revenues		1,035.3	1,078.8
Net income		86	82.9
Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Revenues Including Intersegment Revenues		206.3	264.3
Net income		23.3	28.7
All Other
Segment Reporting Information [Line Items]
Net income		(2.3)	1.6
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	[1],[2]	1,250.5	1,350.9
Total revenues | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	[1]	1,035.2	1,078.7
Total revenues | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	[2]	206.1	264
Total revenues | All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue		8.9	7.8
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue		(0.3)	(0.4)
Intersegment Eliminations | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric		0.1	0.1
Intersegment Eliminations | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		$ 0.2	$ 0.3
[1]	Operating revenues include $109.6 million and $120.1 million of affiliate electric revenue for the three months ended March 31, 2020 and 2019 .
[2]	Operating revenues includes an immaterial amount of affiliate gas revenue for the three months ended March 31, 2020 and 2019 .