Northern States Power 10-Q 26 Apr 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	NORTHERN STATES POWER CO /WI/
Entity Central Index Key	0000072909
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		933,000
Entity Current Reporting Status	Yes

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2017	$ 876,600	$ 93,300	$ 449,400	$ 334,000	$ (100)
Balance (in shares) at Dec. 31, 2017		933,000
Increase (Decrease) in Stockholder's Equity
Net income	31,400			31,400
Other comprehensive income	0				0
Common dividends declared to parent	(16,000)			(16,000)
Contribution of capital by parent	0		0
Ending Balance at Mar. 31, 2018	892,000	$ 93,300	449,400	349,400	(100)
Balance (in shares) at Mar. 31, 2018		933,000
Beginning Balance at Dec. 31, 2018	$ 942,400	$ 93,300	510,100	339,000	0
Balance (in shares) at Dec. 31, 2018	933,000	933,000
Increase (Decrease) in Stockholder's Equity
Net income	$ 24,000			24,000
Other comprehensive income	0				0
Common dividends declared to parent	(24,400)			(24,400)
Contribution of capital by parent	0		0
Ending Balance at Mar. 31, 2019	$ 942,000	$ 93,300	$ 510,100	$ 338,600	$ 0
Balance (in shares) at Mar. 31, 2019	933,000	933,000

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Total operating revenues	$ 276,200	$ 273,100
Operating expenses
Related Party Transaction, Utilities Operating Expense, Purchased Power	103,500	101,300
Operating and maintenance expenses	52,000	50,300
Conservation expenses	3,000	3,000
Depreciation and amortization	34,000	30,600
Taxes (other than income taxes)	7,500	7,300
Total operating expenses	234,200	224,100
Operating income	42,000	49,000
Interest charges and financing costs
Interest charges — includes other financing costs of $0.3 and $0.5 respectively	10,000	9,600
Allowance for funds used during construction — debt	(300)	(800)
Total interest charges and financing costs	9,700	8,800
Other expense, net	(400)	(400)
Allowance for funds used during construction — equity	600	1,900
Income before income taxes	32,500	41,700
Income taxes	8,500	10,300
Net income	24,000	31,400
Electric, non-affiliates
Total operating revenues	170,900	178,700
Affiliate Revenue	44,100	37,600
Operating expenses
Electric fuel and purchased power, non afiiliates	1,900	2,900
Natural gas
Total operating revenues	61,100	56,500
Operating expenses
Electric fuel and purchased power, non afiiliates	32,300	28,700
Other
Total operating revenues	$ 100	$ 300

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Interest charges and financing costs
Other financing costs	$ 300	$ 500

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Comprehensive income:
Net income	$ 24,000	$ 31,400
Derivative instruments:
Reclassification of losses to net income, net of tax of $0 and $0, respectively	0	0
Other comprehensive income	0	0
Comprehensive income	$ 24,000	$ 31,400

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative instruments:
Reclassification of losses to net income, tax	$ 0	$ 0

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net income	$ 24,000	$ 31,400
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	34,300	31,000
Deferred income taxes	(200)	1,800
Amortization of investment tax credits	(100)	100
Allowance for equity funds used during construction	(600)	(1,900)
Changes in operating assets and liabilities:
Accounts receivable	(12,600)	(9,500)
Accrued unbilled revenues	10,600	12,000
Inventories	4,700	6,100
Other current assets	10,700	5,900
Accounts payable	(8,800)	(15,900)
Net regulatory assets and liabilities	3,700	10,500
Other current liabilities	6,100	(1,800)
Pension and other employee benefit obligations	(7,400)	(9,200)
Net cash provided by operating activities	64,600	60,700
Increase (Decrease) in Other Operating Assets and Liabilities, Net	200	200
Investing activities
Utility capital/construction expenditures	(50,400)	(56,600)
Other, net	(100)	(200)
Net cash used in investing activities	(50,500)	(56,800)
Financing activities
(Repayments of) and proceeds from short-term borrowings, net	(2,000)	11,000
Repayments of long-term debt	(100)	0
Capital contributions from parent	14,900	3,300
Dividends paid to parent	(27,400)	(15,500)
Other, net	0	(300)
Net cash provided by (used in) financing activities	(14,600)	(1,500)
Net change in cash and cash equivalents	(500)	2,400
Cash and cash equivalents at beginning of period	2,200	1,400
Cash and cash equivalents at end of period	1,700	3,800
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(10,400)	(5,800)
Cash (paid) received for income taxes, net	6,500	(7,000)
Supplemental disclosure of non-cash investing transactions:
Accrued property, plant and equipment additions	9,000	27,300
Inventory transfers to plant, property and equipment	700	1,300
Allowance for equity funds used during construction	$ 600	$ 1,900

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 1,700	$ 2,200
Accounts receivable, net	72,900	75,100
Accrued unbilled revenues	45,600	56,200
Other Receivables	6,700	6,800
Inventories	11,700	17,100
Regulatory assets	21,500	22,600
Prepaid taxes	18,300	30,200
Prepayments and other	4,100	3,300
Total current assets	182,500	213,500
Property, Plant and Equipment, Net [Abstract]
Property, plant and equipment	2,249,400	2,241,600
Other assets
Regulatory assets	282,000	285,500
Other investments	2,800	2,700
Other	200	200
Total other assets	285,000	288,400
Total assets	2,716,900	2,743,500
Current liabilities
Short-term debt	49,000	51,000
Notes payable to affiliates	0	600
Accounts payable	29,000	56,800
Accounts payable to affiliates	21,800	20,000
Dividends payable to parent	14,400	17,400
Regulatory liabilities	23,900	20,900
Taxes Payable, Current	12,000	3,000
Environmental liabilities	11,500	10,900
Accrued interest	7,700	8,800
Other	12,600	14,800
Total current liabilities	181,900	204,200
Deferred credits and other liabilities
Deferred income taxes	280,300	280,700
Deferred investment tax credits	6,900	7,000
Regulatory liabilities	404,200	400,100
Environmental liabilities	17,000	18,000
Customer advances	16,600	16,800
Pension and employee benefit obligations	37,000	44,500
Other	23,400	22,300
Total deferred credits and other liabilities	785,400	789,400
Commitments and contingencies
Capitalization
Long-term debt	807,600	807,500
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at March 31, 2019 and Dec. 31, 2018, respectively	93,300	93,300
Additional paid in capital	510,100	510,100
Retained earnings	338,600	339,000
Total common stockholder’s equity	942,000	942,400
Total liabilities and equity	$ 2,716,900	$ 2,743,500

CONSOLIDATED BALANCE SHEETS (_2

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Capitalization
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, par value (in dollars per share)	$ 100	$ 100
Common stock, shares outstanding (in shares)	933,000	933,000

Management's Opinion

Management's Opinion	3 Months Ended
	Mar. 31, 2019
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 accounting principles generally accepted in the United States of America (GAAP), the financial position of NSP-Wisconsin and its subsidiaries as of March 31, 2019 and Dec. 31, 2018 ; the results of its operations, including the components of net income, change in stockholders' equity and comprehensive income for the three months ended March 31, 2019 and 2018; and its cash flows for the three months ended March 31, 2019 and 2018. All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after March 31, 2019 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, 2018 balance sheet information has been derived from the audited 2018 consolidated financial statements included in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2018 . 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-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2018 , filed with the SEC on Feb. 22, 2019. Due to the seasonality of NSP-Wisconsin’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, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The significant accounting policies set forth in Note 1 to the consolidated financial statements in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2018 , 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, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Accounting Pronouncements	Accounting Pronouncements Recently Issued Credit Losses — In 2016, the FASB issued Financial Instruments - Credit Losses, Topic 326 (ASC Topic 326), which changes how entities account for credit losses on receivables and certain other assets. The guidance requires use of a current expected loss model, which may result in earlier recognition of credit losses than under previous accounting standards. ASC Topic 326 is effective for interim and annual periods beginning on or after Dec. 15, 2019. NSP-Wisconsin is currently evaluating the impact of adoption of the new standard on its consolidated financial statements. Recently Adopted Leases — In 2016, the FASB issued Leases , Topic 842 (ASC Topic 842) , which provides new accounting and disclosure guidance for leasing activities, most significantly requiring that operating leases be recognized on the balance sheet. NSP-Wisconsin adopted the guidance on Jan. 1, 2019 utilizing the package of transition practical expedients provided by the new standard, including carrying forward prior conclusions on whether agreements existing before the adoption date contain leases and whether existing leases are operating or finance leases; ASC Topic 842 refers to capital leases as finance leases. Specifically for land easement contracts, NSP-Wisconsin has elected the practical expedient provided by ASU No. 2018-01 Leases: Land Easement Practical Expedient for Transition to Topic 842 , and as a result, only those easement contracts entered on or after Jan. 1, 2019 will be evaluated to determine if lease treatment is appropriate. NSP-Wisconsin also utilized the transition practical expedient offered by ASU No. 2018-11 Leases: Targeted Improvements to implement the standard on a prospective basis. As a result, reporting periods in the consolidated financial statements beginning Jan. 1, 2019 reflect the implementation of ASC Topic 842, while prior periods continue to be reported in accordance with Leases, Topic 840 (ASC Topic 840) . The impact of implementing ASC Topic 842 on NSP-Wisconsin's financial statements was insignificant; no amounts were recorded to the consolidated balance sheet as a result of its adoption.

Selected Balance Sheet Data

Selected Balance Sheet Data	3 Months Ended
	Mar. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	(Millions of Dollars) March 31, 2019 Dec. 31, 2018 Accounts receivable, net Accounts receivable $ 78.5 $ 80.7 Less allowance for bad debts (5.6 ) (5.6 ) $ 72.9 $ 75.1 (Millions of Dollars) March 31, 2019 Dec. 31, 2018 Inventories Materials and supplies $ 7.0 $ 6.7 Fuel 3.6 3.8 Natural gas 1.1 6.6 $ 11.7 $ 17.1 (Millions of Dollars) March 31, 2019 Dec. 31, 2018 Property, plant and equipment, net Electric plant $ 2,910.1 $ 2,895.5 Natural gas plant 348.3 345.7 Common and other property 188.6 189.7 Construction work in progress 66.5 55.0 Total property, plant and equipment 3,513.5 3,485.9 Less accumulated amortization (1,264.1 ) (1,244.3 ) $ 2,249.4 $ 2,241.6

Borrowings and Other Financing

Borrowings and Other Financing Instruments	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Borrowings and Other Financing Instruments	Borrowings and Other Financing Instruments NSP-Wisconsin meets its short-term liquidity requirements primarily through the issuance of commercial paper and borrowings under its credit facility. Commercial Paper — Commercial paper outstanding for NSP-Wisconsin was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2019 Year Ended Dec. 31, 2018 Borrowing limit $ 150 $ 150 Amount outstanding at period end 49 51 Average amount outstanding 52 28 Maximum amount outstanding 71 103 Weighted average interest rate, computed on a daily basis 2.71 % 2.31 % Weighted average interest rate at period end 2.67 2.89 Letters of Credit — NSP-Wisconsin uses letters of credit, generally with terms of one year , to provide financial guarantees for certain operating obligations. At March 31, 2019 and Dec. 31, 2018 , there were no letters of credit outstanding. Credit Facility — In order to use its commercial paper program to fulfill short-term funding needs, NSP-Wisconsin must have a revolving credit facility in place at least equal to the amount of its commercial paper borrowing limit and cannot issue commercial paper in an aggregate amount exceeding available capacity under this credit facility. The 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. As of March 31, 2019 , NSP-Wisconsin had the following committed credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 150 $ 49 $ 101 (a) This credit facility expires in June 2021 . (b) Includes outstanding commercial paper. All credit facility bank borrowings, outstanding letters of credit and outstanding commercial paper reduce the available capacity under the credit facility. NSP-Wisconsin had no direct advances on the credit facility outstanding at March 31, 2019 and Dec. 31, 2018 . Other Short-Term Borrowings — The following table presents the notes payable of Clearwater Investments, Inc., a NSP-Wisconsin subsidiary, to Xcel Energy Inc.: (Amounts in Millions, Except Interest Rates) March 31, 2019 Dec. 31, 2018 Notes payable to affiliates $ — $ 0.6 Weighted average interest rate at period end N/A 2.89 %

Revenues

Revenues	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenues	Revenues Revenue is classified by the type of goods/services rendered and market/customer type. NSP-Wisconsin’s operating revenues consists of the following: Three Months Ended March 31, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 67.4 $ 33.6 $ — $ 101.0 Commercial and industrial (C&I) 98.5 25.8 — 124.3 Other 1.5 — 0.1 1.6 Total retail 167.4 59.4 0.1 226.9 Interchange 44.1 — — 44.1 Other 0.5 1.1 — 1.6 Total revenue from contracts with customers 212.0 60.5 0.1 272.6 Alternative revenue and other 3.0 0.6 — 3.6 Total revenues $ 215.0 $ 61.1 $ 0.1 $ 276.2 Three Months Ended March 31, 2018 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 67.8 $ 30.3 $ — $ 98.1 C&I 104.8 24.6 0.1 129.5 Other 1.6 — 0.2 1.8 Total retail 174.2 54.9 0.3 229.4 Interchange 37.7 — — 37.7 Other 1.5 1.0 — 2.5 Total revenue from contracts with customers 213.4 55.9 0.3 269.6 Alternative revenue and other 2.9 0.6 — 3.5 Total revenues $ 216.3 $ 56.5 $ 0.3 $ 273.1

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Except to the extent noted below, Note 7 to the consolidated financial statements included in NSP-Wisconsin’s Annual Report on Form 10-K for the year ended Dec. 31, 2018 appropriately represents, in all material respects, the current status of other income tax matters, and are incorporated herein by reference. Total income tax expense from operations differs from the amount computed by applying the statutory federal income tax rate to income before income tax expense. The following reconciles such differences: Three Months Ended March 31 2019 2018 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 6.2 6.2 Increases (decreases) in tax from: Regulatory differences (a) (0.5 ) (1.8 ) Tax credits and allowances (net) (0.8 ) (0.8 ) Other (net) 0.3 0.1 Effective income tax rate 26.2 % 24.7 % (a) Regulatory differences for income tax purposes primarily include the average rate assumption method (ARAM), ARAM deferral and AFUDC - Equity. ARAM is a method to flow back excess deferred taxes to customers. ARAM has been deferred when regulatory treatment has not been established. As Xcel Energy received direction from its regulatory commissions regarding the return of excess deferred taxes to customers, the ARAM deferral was reversed. This resulted in a reduction to tax expense with a corresponding reduction to revenue. Federal Audits — NSP-Wisconsin 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 consolidated federal income tax returns expire as follows: Tax Year(s) Expiration 2009 - 2013 October 2019 2014 - 2016 September 2020 2017 September 2021 In the third quarter of 2015, the IRS commenced an examination of tax years 2012 and 2013 . In the third quarter of 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, 2019 , 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 the fourth quarter of 2018, the IRS began an audit of tax year 2014-2016 . As of March 31, 2019 no adjustments have been proposed. State Audits — NSP-Wisconsin is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of March 31, 2019 , NSP-Wisconsin’s earliest open tax year that is subject to examination by state taxing authorities under applicable statutes of limitations is 2014 . In the fourth quarter of 2018, Wisconsin began an audit of tax years 2014-2016 . As of March 31, 2019 no material adjustments have been proposed. 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 the 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, 2019 Dec. 31, 2018 Unrecognized tax benefit — Permanent tax positions $ 2.0 $ 2.0 Unrecognized tax benefit — Temporary tax positions 0.9 0.8 Total unrecognized tax benefit $ 2.9 $ 2.8 Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards: (Millions of Dollars) March 31, 2019 Dec. 31, 2018 NOL and tax credit carryforwards $ (2.0 ) $ (2.1 ) Net deferred tax liability associated with the unrecognized tax benefit amounts and related NOLs and tax credits carryforwards were $1.0 million and $1.1 million for March 31, 2019 and Dec. 31, 2018, respectively. As the IRS Appeals and federal and state audits progress, it is reasonably possible that the amount of unrecognized tax benefit could decrease up to approximately $2.2 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. Payables for interest related to unrecognized tax benefits at March 31, 2019 and Dec. 31, 2018 were not material. No amounts were accrued for penalties related to unrecognized tax benefits as of March 31, 2019 or Dec. 31, 2018.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	Fair Value of Financial Assets and Liabilities Fair Value Measurements The 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. 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 NAVs. 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 generally utilize observable forward prices and volatilities, as well as observable pricing adjustments for specific delivery locations, and are generally assigned a Level 2 classification. When contractual settlements relate to delivery locations for which pricing is relatively unobservable, or extend to periods beyond those readily observable on active exchanges or quoted by brokers, the significance of the use of less observable inputs on a valuation is evaluated, and may result in Level 3 classification. Derivative Instruments Fair Value Measurements NSP-Wisconsin 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 and utility commodity prices. Interest Rate Derivatives — NSP-Wisconsin may enter 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, 2019 , accumulated other comprehensive loss related to interest rate derivatives included no net gains or losses expected to be reclassified into earnings during the next 12 months as the related hedged interest rate transactions impact earnings, including forecasted amounts for unsettled hedges, as applicable. Commodity Derivatives — NSP-Wisconsin may enter 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 natural gas to generate electric energy and natural gas for resale. Gross notional amounts of commodity options: (Amounts in Millions) (a)(b) March 31, 2019 Dec. 31, 2018 MMBtu of natural gas — 1.2 (a) Amounts are not reflective of net positions in the underlying commodities. (b) Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise. Consideration of Credit Risk and Concentrations — NSP-Wisconsin 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. Impact of Derivative Activities on Income and Accumulated Other Comprehensive Loss — There were no pre-tax gains or losses related to interest rate derivatives reclassified from accumulated other comprehensive loss into earnings for the three months ended March, 31 2019 and an immaterial amount of pre-tax losses for the three months ended March 31, 2018. Changes in the fair value of natural gas commodity derivatives resulted in net gains of $0.1 million and immaterial net losses for the three months ended March 31, 2019 and 2018, respectively, recognized as regulatory assets and liabilities. The classification as a regulatory asset or liability is based on commission approved regulatory recovery mechanisms. During the three months ended March 31, 2019 and 2018, $0.2 million of natural gas commodity derivatives settlement gains and no gains or losses, respectively, were recognized subject to purchased natural gas cost recovery mechanisms, which result in reclassifications of derivative settlement gains and losses out of income to a regulatory asset or liability, as appropriate. NSP-Wisconsin had no derivative instruments designated as fair value hedges during the three months ended March 31, 2019 and 2018 . Recurring Fair Value Measurements — The following tables presents for each of the fair value hierarchy levels, NSP-Wisconsin's derivative assets and liabilities measured at fair value on a recurring basis: March 31, 2019 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ — $ — $ — $ — $ — Dec. 31, 2018 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ 0.2 $ — $ 0.2 $ — $ 0.2 (a) NSP-Wisconsin 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, 2019 and Dec. 31, 2018 . The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) Included in prepayments and other current assets balance of $4.1 million at March 31, 2019 and $3.3 million at Dec. 31, 2018 in the consolidated balance sheets. Fair Value of Long-Term Debt Other financial instruments for which the carrying amount did not equal fair value: March 31, 2019 Dec. 31, 2018 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 807.6 $ 878.6 $ 807.5 $ 850.4 Fair value of NSP-Wisconsin’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, 2019 and Dec. 31, 2018 , 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, 2019
Retirement Benefits [Abstract]
Benefit Plans and Other Postretirement Benefits	Benefit Plans and Other Postretirement Benefits Components of Net Periodic Benefit Cost Three Months Ended March 31 2019 2018 2019 2018 (Millions of Dollars) Pension Benefits Postretirement Health Care Benefits Service cost $ 1.1 $ 1.2 $ — $ — Interest cost (a) 1.4 1.4 0.1 0.2 Expected return on plan assets (a) (2.1 ) (2.3 ) — — Amortization of prior service (credit) cost (a) — — (0.1 ) (0.1 ) Amortization of net loss (a) 1.1 1.4 0.1 0.1 Settlement charge — — — — Net periodic benefit cost 1.5 1.7 0.1 0.2 Costs not recognized due to the effects of regulation 0.2 0.2 — — Net benefit cost recognized for financial reporting $ 1.7 $ 1.9 $ 0.1 $ 0.2 (a) The components of net periodic cost other than the service cost component are included in the line item “other expense, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset. In January 2019, contributions of $150 million were made across four of Xcel Energy’s pension plans, of which $7 million was attributable to NSP-Wisconsin. Xcel Energy does not expect additional pension contributions during 2019.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The following include commitments, contingencies and unresolved contingencies that are material to NSP-Wisconsin’s financial position. Legal Contingencies NSP-Wisconsin is involved in various litigation matters that are being defended and handled 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 complex judgments about future events. Management maintains accruals for losses that are 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 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, arising from such current proceedings would have a material effect on NSP-Wisconsin’s financial statements. Unless otherwise required by GAAP, legal fees are expensed as incurred. Gas Trading Litigation — e prime is a wholly owned subsidiary of Xcel Energy. e prime was in the business of natural gas trading and marketing but has not engaged in natural gas trading or marketing activities since 2003. Multiple lawsuits seeking monetary damages were commenced against e prime and its affiliates, including Xcel Energy, between 2003 and 2009 alleging fraud and anticompetitive activities in conspiring to restrain the trade of natural gas and manipulate natural gas prices. Cases were all consolidated in the U.S. District Court in Nevada. Two cases remain active which include an MDL matter consisting of a Colorado purported class (Breckenridge) and a Wisconsin purported class (Arandell Corp.). Breckenridge/Colorado - The MDL panel remanded Breckenridge back to the U.S. District Court in Colorado. Arandell Corp. - Xcel Energy has filed a no opposition motion to have the case remanded back to the U.S. District Court in Wisconsin. The motion will be heard in May 2019. Xcel Energy has concluded that a loss is remote for both remaining lawsuits. Rate Matters 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. In October 2018, the FERC issued an ROE order that addressed the D.C. Circuit’s actions. Under a new proposed two step ROE approach, the FERC indicated an intention to dismiss an ROE complaint if the existing ROE falls within the range of just and reasonable ROEs based on equal weighting of the DCF, CAPM, and Expected Earnings models. The FERC proposed that if necessary, it would then set a new ROE by averaging the results of these models plus a Risk Premium model. The FERC subsequently made preliminary determinations in a November 2018 order that the MISO TO's base ROE in effect for the first complaint period ( 12.38% ) was outside the range of reasonableness, and should be reduced. The FERC indicated its preliminary analysis using the new ROE approach resulted in a base ROE of 10.28% for the first complaint period, compared to the previously ordered base ROE of 10.32% . FERC ordered additional briefings on the new methodology, which were filed in February and April 2019. The FERC is expected to act no earlier than the second half of 2019. NSP-Minnesota has recognized a current refund liability consistent with its best estimate of the final ROE. 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. Initial comments on both NOIs are due in June 2019, with reply comments due in July 2019. No final FERC action is expected before the second half of 2019. Environmental MGP Sites Ashland MGP Site — NSP-Wisconsin was named a responsible party for contamination at the Ashland/Northern States Power Lakefront Superfund Site (the Site) in Ashland, Wisconsin. Remediation and restoration activities are anticipated to be completed in 2019 and groundwater treatment activities will continue for many years. The current cost estimate for remediation and restoration of the entire site is approximately $190 million . At both March 31, 2019 and Dec. 31, 2018, NSP-Wisconsin had a total liability of $27 million for the entire site. NSP-Wisconsin has deferred the unrecovered portion of the estimated Site remediation costs as a regulatory asset. The PSCW has authorized NSP-Wisconsin rate recovery for all remediation costs incurred at the Site. In 2012, the PSCW agreed to allow NSP-Wisconsin to pre-collect certain costs, to amortize costs over 10 years and to apply a 3% carrying cost to the unamortized regulatory asset. MGP, Landfill or Disposal Sites — NSP-Wisconsin is currently investigating or remediating two MGP, landfill or other disposal sites across its service territories, in addition to the Ashland MGP Site, and these activities will continue through at least 2020. NSP-Wisconsin accrued $1.7 million as of March 31, 2019 and Dec. 31, 2018, respectively, for these sites. There may be insurance recovery and/or recovery from other potentially responsible parties, offsetting a portion of the costs incurred.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information Operating results from regulated electric utility and regulated natural gas utility are each separately and regularly reviewed by NSP-Wisconsin’s chief operating decision maker. NSP-Wisconsin 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-Wisconsin has the following reportable segments: • Regulated Electric - The regulated electric utility segment generates electricity which is transmitted and distributed in Wisconsin and Michigan. • Regulated Natural Gas - The regulated natural gas utility segment purchases, transports, stores and distributes natural gas in portions of Wisconsin and Michigan. • All Other - revenues from operating segments not included above are below the necessary quantitative thresholds and are therefore included in the all other category. Those primarily include investments in rental housing projects that qualify for low-income housing tax credits. Asset and capital expenditure information is not provided for NSP-Minnesota’s reportable segments because as an integrated electric and natural gas utility, NSP-Minnesota operates significant assets that are not dedicated to a specific business segment, and reporting assets and capital expenditures by business segment would require arbitrary and potentially misleading allocations which may not necessarily reflect the assets that would be required for the operation of the business segments on a stand-alone basis. 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-Wisconsin's segment information for the three months ended March 31: (Millions of Dollars) 2019 2018 Regulated Electric Operating revenues (a) $ 215.0 $ 216.3 Intersegment revenues 0.1 0.1 Total operating revenue 215.1 216.4 Net income 13.2 20.4 Regulated Natural Gas Operating revenues (a) $ 61.1 $ 56.5 Intersegment revenues 0.2 0.1 Total operating revenue 61.3 56.6 Net income 10.5 10.4 All Other Operating revenues (a) $ 0.1 $ 0.3 Intersegment revenues — — Total operating revenue 0.1 0.3 Net income 0.3 0.6 Consolidated Total Operating revenues (a) $ 276.5 $ 273.3 Reconciling Eliminations (0.3 ) (0.2 ) Total operating revenue 276.2 273.1 Net income 24.0 31.4 (a) Operating revenues include $44.1 million and $37.7 million of affiliate electric revenue for the three months ended March 31, 2019 and 2018, respectively.

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	3 Months Ended
	Mar. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net	(Millions of Dollars) March 31, 2019 Dec. 31, 2018 Accounts receivable, net Accounts receivable $ 78.5 $ 80.7 Less allowance for bad debts (5.6 ) (5.6 ) $ 72.9 $ 75.1
Inventories	(Millions of Dollars) March 31, 2019 Dec. 31, 2018 Inventories Materials and supplies $ 7.0 $ 6.7 Fuel 3.6 3.8 Natural gas 1.1 6.6 $ 11.7 $ 17.1
Property, Plant and Equipment, Net	(Millions of Dollars) March 31, 2019 Dec. 31, 2018 Property, plant and equipment, net Electric plant $ 2,910.1 $ 2,895.5 Natural gas plant 348.3 345.7 Common and other property 188.6 189.7 Construction work in progress 66.5 55.0 Total property, plant and equipment 3,513.5 3,485.9 Less accumulated amortization (1,264.1 ) (1,244.3 ) $ 2,249.4 $ 2,241.6

Borrowings and Other Financin_2

Borrowings and Other Financing Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	As of March 31, 2019 , NSP-Wisconsin had the following committed credit facility available (in millions of dollars): Credit Facility (a) Outstanding (b) Available $ 150 $ 49 $ 101 (a) This credit facility expires in June 2021 . (b) Includes outstanding commercial paper.
Commercial Paper
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Commercial paper outstanding for NSP-Wisconsin was as follows: (Amounts in Millions, Except Interest Rates) Three Months Ended March 31, 2019 Year Ended Dec. 31, 2018 Borrowing limit $ 150 $ 150 Amount outstanding at period end 49 51 Average amount outstanding 52 28 Maximum amount outstanding 71 103 Weighted average interest rate, computed on a daily basis 2.71 % 2.31 % Weighted average interest rate at period end 2.67 2.89
Notes Payable To Affiliates
Borrowings and Other Financing Instruments [Abstract]
Short-Term Borrowings	Other Short-Term Borrowings — The following table presents the notes payable of Clearwater Investments, Inc., a NSP-Wisconsin subsidiary, to Xcel Energy Inc.: (Amounts in Millions, Except Interest Rates) March 31, 2019 Dec. 31, 2018 Notes payable to affiliates $ — $ 0.6 Weighted average interest rate at period end N/A 2.89 %

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	NSP-Wisconsin’s operating revenues consists of the following: Three Months Ended March 31, 2019 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 67.4 $ 33.6 $ — $ 101.0 Commercial and industrial (C&I) 98.5 25.8 — 124.3 Other 1.5 — 0.1 1.6 Total retail 167.4 59.4 0.1 226.9 Interchange 44.1 — — 44.1 Other 0.5 1.1 — 1.6 Total revenue from contracts with customers 212.0 60.5 0.1 272.6 Alternative revenue and other 3.0 0.6 — 3.6 Total revenues $ 215.0 $ 61.1 $ 0.1 $ 276.2 Three Months Ended March 31, 2018 (Millions of Dollars) Electric Natural Gas All Other Total Major revenue types Revenue from contracts with customers: Residential $ 67.8 $ 30.3 $ — $ 98.1 C&I 104.8 24.6 0.1 129.5 Other 1.6 — 0.2 1.8 Total retail 174.2 54.9 0.3 229.4 Interchange 37.7 — — 37.7 Other 1.5 1.0 — 2.5 Total revenue from contracts with customers 213.4 55.9 0.3 269.6 Alternative revenue and other 2.9 0.6 — 3.5 Total revenues $ 216.3 $ 56.5 $ 0.3 $ 273.1

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Total income tax expense from operations differs from the amount computed by applying the statutory federal income tax rate to income before income tax expense. The following reconciles such differences: Three Months Ended March 31 2019 2018 Federal statutory rate 21.0 % 21.0 % State tax (net of federal tax effect) 6.2 6.2 Increases (decreases) in tax from: Regulatory differences (a) (0.5 ) (1.8 ) Tax credits and allowances (net) (0.8 ) (0.8 ) Other (net) 0.3 0.1 Effective income tax rate 26.2 % 24.7 % (a) Regulatory differences for income tax purposes primarily include the average rate assumption method (ARAM), ARAM deferral and AFUDC - Equity. ARAM is a method to flow back excess deferred taxes to customers. ARAM has been deferred when regulatory treatment has not been established. As Xcel Energy received direction from its regulatory commissions regarding the return of excess deferred taxes to customers, the ARAM deferral was reversed. This resulted in a reduction to tax expense with a corresponding reduction to revenue.
Summary of Statute of Limitations Applicable to Open Tax Years [Table Text Block]	Federal Audits — NSP-Wisconsin 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 consolidated federal income tax returns expire as follows: Tax Year(s) Expiration 2009 - 2013 October 2019 2014 - 2016 September 2020 2017 September 2021
Reconciliation of Unrecognized Tax Benefits	Unrecognized tax benefits - permanent vs. temporary: (Millions of Dollars) March 31, 2019 Dec. 31, 2018 Unrecognized tax benefit — Permanent tax positions $ 2.0 $ 2.0 Unrecognized tax benefit — Temporary tax positions 0.9 0.8 Total unrecognized tax benefit $ 2.9 $ 2.8
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, 2019 Dec. 31, 2018 NOL and tax credit carryforwards $ (2.0 ) $ (2.1 )

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Gross Notional Amounts of Commodity Forwards and Options	Gross notional amounts of commodity options: (Amounts in Millions) (a)(b) March 31, 2019 Dec. 31, 2018 MMBtu of natural gas — 1.2 (a) Amounts are not reflective of net positions in the underlying commodities. (b) Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.
Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level	Recurring Fair Value Measurements — The following tables presents for each of the fair value hierarchy levels, NSP-Wisconsin's derivative assets and liabilities measured at fair value on a recurring basis: March 31, 2019 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ — $ — $ — $ — $ — Dec. 31, 2018 Fair Value Fair Value Total Netting (a) Total (b) (Millions of Dollars) Level 1 Level 2 Level 3 Current derivative assets Natural gas commodity $ — $ 0.2 $ — $ 0.2 $ — $ 0.2 (a) NSP-Wisconsin 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, 2019 and Dec. 31, 2018 . The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements. (b) Included in prepayments and other current assets balance of $4.1 million at March 31, 2019 and $3.3 million at Dec. 31, 2018 in the consolidated balance sheets.
Carrying Amount and Fair Value of Long-term Debt	Other financial instruments for which the carrying amount did not equal fair value: March 31, 2019 Dec. 31, 2018 (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current portion $ 807.6 $ 878.6 $ 807.5 $ 850.4

Benefit Plans and Other Postr_2

Benefit Plans and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost	Components of Net Periodic Benefit Cost Three Months Ended March 31 2019 2018 2019 2018 (Millions of Dollars) Pension Benefits Postretirement Health Care Benefits Service cost $ 1.1 $ 1.2 $ — $ — Interest cost (a) 1.4 1.4 0.1 0.2 Expected return on plan assets (a) (2.1 ) (2.3 ) — — Amortization of prior service (credit) cost (a) — — (0.1 ) (0.1 ) Amortization of net loss (a) 1.1 1.4 0.1 0.1 Settlement charge — — — — Net periodic benefit cost 1.5 1.7 0.1 0.2 Costs not recognized due to the effects of regulation 0.2 0.2 — — Net benefit cost recognized for financial reporting $ 1.7 $ 1.9 $ 0.1 $ 0.2 (a) The components of net periodic cost other than the service cost component are included in the line item “other expense, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Guarantees Issued and Outstanding	.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Results from Operations by Reportable Segment	NSP-Wisconsin's segment information for the three months ended March 31: (Millions of Dollars) 2019 2018 Regulated Electric Operating revenues (a) $ 215.0 $ 216.3 Intersegment revenues 0.1 0.1 Total operating revenue 215.1 216.4 Net income 13.2 20.4 Regulated Natural Gas Operating revenues (a) $ 61.1 $ 56.5 Intersegment revenues 0.2 0.1 Total operating revenue 61.3 56.6 Net income 10.5 10.4 All Other Operating revenues (a) $ 0.1 $ 0.3 Intersegment revenues — — Total operating revenue 0.1 0.3 Net income 0.3 0.6 Consolidated Total Operating revenues (a) $ 276.5 $ 273.3 Reconciling Eliminations (0.3 ) (0.2 ) Total operating revenue 276.2 273.1 Net income 24.0 31.4 (a) Operating revenues include $44.1 million and $37.7 million of affiliate electric revenue for the three months ended March 31, 2019 and 2018, respectively.

Selected Balance Sheet Data, Ac

Selected Balance Sheet Data, Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts Receivable, Net
Accounts receivable	$ 78,500	$ 80,700
Less allowance for bad debts	(5,600)	(5,600)
Accounts receivable, net	$ 72,900	$ 75,100

Selected Balance Sheet Data, In

Selected Balance Sheet Data, Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Public Utilities, Inventory [Line Items]
Inventories	$ 11,700	$ 17,100
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	7,000	6,700
Fuel
Public Utilities, Inventory [Line Items]
Inventories	3,600	3,800
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 1,100	$ 6,600

Selected Balance Sheet Data, Pr

Selected Balance Sheet Data, Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 3,513,500	$ 3,485,900
Less accumulated depreciation	(1,264,100)	(1,244,300)
Property, plant and equipment, net	2,249,400	2,241,600
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,910,100	2,895,500
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	348,300	345,700
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	188,600	189,700
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 66,500	$ 55,000

Borrowings and Other Financin_3

Borrowings and Other Financing Instruments, Commercial Paper (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Amount outstanding at period end	$ 49,000,000	$ 51,000,000
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	150,000,000	150,000,000
Amount outstanding at period end	49,000,000	51,000,000
Average amount outstanding	52,000,000	28,000,000
Maximum amount outstanding	$ 71,000,000	$ 103,000,000
Weighted average interest rate, computed on a daily basis (percentage)	2.71%	2.31%
Weighted average interest rate at period end (percentage)	2.67%	2.89%

Borrowings and Other Financin_4

Borrowings and Other Financing Instruments, Letters of Credit (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 49,000	$ 51,000
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end	$ 0	$ 0
Letter of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Term of letters of credit (in years)	1 year

Borrowings and Other Financin_5

Borrowings and Other Financing Instruments, Credit Facility (Details) - Credit Facility - USD ($)		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 150,000,000
Drawn	[2]	49,000,000
Available		$ 101,000,000
Maturity Date		Jun. 30, 2021
Direct advances on the credit facility outstanding		$ 0	$ 0
[1]	This credit facility expires in June 2021.
[2]	Includes outstanding commercial paper.

Borrowings and Other Financin_6

Borrowings and Other Financing Instruments, Intercompany Borrowing Arrangement and Other Short-Term Borrowings (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Notes payable to affiliates	$ 0	$ 600
Notes Payable To Affiliates
Short-term Debt [Line Items]
Notes payable to affiliates	$ 0	$ 600
Weighted average interest rate at period end (percentage)		2.89%

Revenues (Details)

Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 276,200	$ 273,100
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	272,600	269,600
Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	226,900	229,400
Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	101,000	98,100
Retail | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	124,300	129,500
Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,600	1,800
Interchange [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	44,100	37,700
Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,600	2,500
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Total operating revenues	3,600	3,500
Regulated Electric | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	212,000	213,400
Regulated Electric | Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	167,400	174,200
Regulated Electric | Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	67,400	67,800
Regulated Electric | Retail | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	98,500	104,800
Regulated Electric | Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,500	1,600
Regulated Electric | Interchange [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	44,100	37,700
Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	500	1,500
Regulated Electric | Alternative revenue and other
Disaggregation of Revenue [Line Items]
Total operating revenues	3,000	2,900
Regulated Natural Gas | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	60,500	55,900
Regulated Natural Gas | Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	59,400	54,900
Regulated Natural Gas | Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	33,600	30,300
Regulated Natural Gas | Retail | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	25,800	24,600
Regulated Natural Gas | Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Regulated Natural Gas | Interchange [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,100	1,000
Regulated Natural Gas | Alternative revenue and other
Disaggregation of Revenue [Line Items]
Total operating revenues	600	600
All Other | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	100	300
All Other | Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	100	300
All Other | Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
All Other | Retail | Commercial and industrial (C&I)
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	100
All Other | Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	100	200
All Other | Interchange [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
All Other | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
All Other | Alternative revenue and other
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Total revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	276,200	273,100
Total revenues | Regulated Electric
Disaggregation of Revenue [Line Items]
Total operating revenues	215,000	216,300
Total revenues | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Total operating revenues	61,100	56,500
Total revenues | All Other
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 100	$ 300

Income Taxes (Details)

Income Taxes (Details) - USD ($)		3 Months Ended				9 Months Ended
		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2015
Income Tax Examination [Line Items]
Net Deferred Tax Liability associated with the Unrecognized Tax Benefit Amounts and Related NOLs and Tax Credit Carryforwards		$ (1,000,000)	$ (1,100,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%		21.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		6.20%		6.20%
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[1]	(0.50%)		(1.80%)
Regulatory difference - reversal of prior quarters' ARAM deferral (b)		(0.80%)		(0.80%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		0.30%		0.10%
Effective Income Tax Rate Reconciliation, Percent		26.20%		24.70%
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit — Permanent tax positions		$ 2,000,000	2,000,000
Unrecognized tax benefit — Temporary tax positions		900,000	800,000
Total unrecognized tax benefit		2,900,000	2,800,000
NOL and tax credit carryforwards		(2,000,000)	(2,100,000)
Upper bound of decrease in unrecognized tax benefit that is reasonably possible		2,200,000
Amounts accrued for penalties related to unrecognized tax benefits		0	$ 0
Internal Revenue Service (IRS)
Tax Audits [Abstract]
Year(s) under examination			2014-2016			2012 and 2013
Tax years under examination, Concluded					2012 and 2013
Potential Tax Adjustments		0
State Jurisdiction (Wisconsin)
Tax Audits [Abstract]
Year(s) under examination			2014-2016
Potential Tax Adjustments		$ 0
Earliest year subject to examination		2014
[1]	Regulatory differences for income tax purposes primarily include the average rate assumption method (ARAM), ARAM deferral and AFUDC - Equity. ARAM is a method to flow back excess deferred taxes to customers. ARAM has been deferred when regulatory treatment has not been established. As Xcel Energy received direction from its regulatory commissions regarding the return of excess deferred taxes to customers, the ARAM deferral was reversed. This resulted in a reduction to tax expense with a corresponding reduction to revenue.

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities, Derivative Instruments (Details) MMBTU in Millions, $ in Millions		Mar. 31, 2019USD ($)MMBTU	Dec. 31, 2018MMBTU
Interest Rate Swap
Derivative [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net | $		$ 0
Natural Gas Commodity (in million British thermal units)
Gross Notional Amounts of Commodity Options [Abstract]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	0	1.2
[1]	Amounts are not reflective of net positions in the underlying commodities.
[2]	Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities, Impact of Derivative Activity (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financial Impact of Qualifying Fair Value Hedges on Earnings [Abstract]
Derivative instruments designated as fair value hedges	$ 0	$ 0
Other Derivative Instruments | Natural Gas Commodity
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities	100,000
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	(200,000)	$ 0
Cash Flow Hedges | Designated as Hedging Instrument | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	$ 0

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities, Derivative Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Prepayments and other		$ 4,100	$ 3,300
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			0
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			0
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	0	200
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[2]	0	0
Fair Value Measured on a Recurring Basis | Level 1 | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	0
Fair Value Measured on a Recurring Basis | Level 2 | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	200
Fair Value Measured on a Recurring Basis | Level 3 | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	0
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis
Derivatives, Fair Value [Line Items]
Prepayments and other		4,100	3,300
Estimate of Fair Value Measurement [Member] | Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 0	$ 200
[1]	Included in prepayments and other current assets balance of $4.1 million at March 31, 2019 and $3.3 million at Dec. 31, 2018 in the consolidated balance sheets.
[2]	NSP-Wisconsin 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, 2019 and Dec. 31, 2018. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities, Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Carrying Amount
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, including current portion	$ 807.6	$ 807.5
Fair Value
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, including current portion	$ 878.6	$ 850.4

Benefit Plans and Other Postr_3

Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands		1 Months Ended	3 Months Ended
		Jan. 31, 2019USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Jan. 01, 2019Plan
Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost			$ 1,100	$ 1,200
Interest cost	[1]		1,400	1,400
Expected return on plan assets	[1]		(2,100)	(2,300)
Amortization of prior service cost (credit)	[1]		0	0
Amortization of net loss	[1]		1,100	1,400
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			0	0
Defined Benefit Plan Net Benefit Cost (Credit) Recognized Before Regulatory Adjustments			1,500	1,700
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation			200	200
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			1,700	1,900
Total contributions to the pension plans during the period		$ 7,000
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost			0	0
Interest cost	[1]		100	200
Expected return on plan assets	[1]		0	0
Amortization of prior service cost (credit)	[1]		(100)	(100)
Amortization of net loss	[1]		100	100
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			0	0
Defined Benefit Plan Net Benefit Cost (Credit) Recognized Before Regulatory Adjustments			100	200
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation			0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			$ 100	$ 200
Xcel Energy Inc. | Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Total contributions to the pension plans during the period		$ 150,000
Number of Xcel Energy's pension plans to which contributions were made | Plan					4
[1]	The components of net periodic cost other than the service cost component are included in the line item “other expense, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.

Commitments and Contingencies,

Commitments and Contingencies, Environmental Contingencies - Site Contingencies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Ashland MGP Site
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Accrual for Environmental Loss Contingencies, Gross		$ 27
Approved amortization period for recovery of remediation costs in natural gas rates (in years)	10 years
Carrying cost percentage to be applied to unamortized regulatory asset	3.00%
Other MGP Sites [Member]
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Accrual for Environmental Loss Contingencies, Gross		$ 1.7
Other MGP, Landfill, or Disposal Sites [Domain]
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Number of identified MGP sites under current investigation and/or remediation in addition to those separately disclosed	2
NSP-Wisconsin | Ashland MGP Site
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Current Cost Estimate for Site Remediation	$ 190

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Legal Contingencies (Details)	Dec. 31, 2018
Gas Trading Litigation
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number	2

Commitments and Contingencies_2

Commitments and Contingencies Commitments and Contingencies, Rate Matters, NSP-Minnesota (Details) - NSP-Minnesota - FERC Proceeding, MISO ROE Complaint	1 Months Ended				12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Feb. 28, 2015	Nov. 30, 2013	Dec. 31, 2018	Dec. 31, 2017
Rate Matters [Abstract]
Public Utilities, Base Return On Equity Charged To Customers Through Transmission Formula Rates			12.38%	12.38%
Public Utilities, ROE developed with new approach					10.28%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Recommended By Third Parties			8.67%	9.15%
Public Utilities, Number of steps required					2
Federal Energy Regulatory Commission (FERC)
Rate Matters [Abstract]
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Approved	10.32%	10.32%
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, with RTO Adder, Approved						10.82%

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Related Party Transaction - Electric and Gas Domestic Regulated Revenue	$ 44,100	$ 37,700
Revenue from Contract with Customer, Excluding Assessed Tax	276,200	273,100
Operating revenues	276,200	273,100
Net income (loss)	24,000	31,400
Regulated Electric
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	215,100	216,400
Net income (loss)	13,200	20,400
Regulated Natural Gas
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	61,300	56,600
Net income (loss)	10,500	10,400
All Other
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	100	300
Net income (loss)	300	600
Total revenues
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	276,500	273,300
Operating revenues	276,200	273,100
Total revenues | Regulated Electric
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	215,000	216,300
Operating revenues	215,000	216,300
Total revenues | Regulated Natural Gas
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	61,100	56,500
Operating revenues	61,100	56,500
Total revenues | All Other
Segment Reporting Information [Line Items]
Operating revenues	100	300
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(300)	(200)
Net income (loss)	24,000	31,400
Intersegment Eliminations | Regulated Electric
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	100	100
Intersegment Eliminations | Regulated Natural Gas
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	200	100
Intersegment Eliminations | All Other
Segment Reporting Information [Line Items]
Operating revenues	$ 0	$ 0