Northern States Power 10-Q 4 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	4-May-15
Document and Entity Information [Abstract]
Entity Registrant Name	NORTHERN STATES POWER CO /WI/
Entity Central Index Key	72909
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		933,000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating revenues
Electric	$210,284	$211,097
Natural gas	63,296	73,791
Other	380	254
Total operating revenues	273,960	285,142
Operating expenses
Electric fuel and purchased power, non-affiliates	1,283	8,851
Purchased power, affiliates	111,832	109,571
Cost of natural gas sold and transported	42,438	51,142
Operating and maintenance expenses	42,173	44,231
Conservation program expenses	2,855	2,672
Depreciation and amortization	21,361	19,307
Taxes (other than income taxes)	7,232	6,797
Loss on Monticello life cycle management/extended power uprate project	5,237	0
Total operating expenses	234,411	242,571
Operating income	39,549	42,571
Other income, net	249	124
Allowance for funds used during construction — equity	2,219	1,572
Interest charges and financing costs
Interest charges — includes other financing costs of $402 and $374, respectively	7,756	6,867
Allowance for funds used during construction — debt	-1,070	-758
Total interest charges and financing costs	6,686	6,109
Income before income taxes	35,331	38,158
Income taxes	13,064	13,923
Net income	$22,267	$24,235

CONSOLIDATED_STATEMENTS_OF_INC1

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (Parenthetical) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Interest charges and financing costs
Other financing costs	$402	$374

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Comprehensive income:
Net income	$22,267	$24,235
Derivative instruments:
Reclassification of losses to net income, net of tax of $13 and $13, respectively	19	18
Other comprehensive income	19	18
Comprehensive income	$22,286	$24,253

CONSOLIDATED_STATEMENTS_OF_COM1

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative instruments:
Reclassification of losses to net income, net of tax	$13	$13

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating activities
Net income	$22,267	$24,235
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	21,682	19,590
Deferred income taxes	8,241	10,069
Amortization of investment tax credits	-132	-168
Allowance for equity funds used during construction	-2,219	-1,572
Loss on Monticello life cycle management/extended power uprate project	5,237	0
Net derivative losses	554	437
Changes in operating assets and liabilities:
Accounts receivable	-5,496	-13,722
Accrued unbilled revenues	10,428	12,194
Inventories	9,830	6,980
Other current assets	11,335	11,145
Accounts payable	-11,851	12,378
Net regulatory assets and liabilities	-1,404	-20,462
Other current liabilities	1,289	2,936
Pension and other employee benefit obligations	-4,915	-8,007
Change in other noncurrent assets	-4	23
Change in other noncurrent liabilities	535	160
Net cash provided by operating activities	65,377	56,216
Investing activities
Utility capital/construction expenditures	-79,926	-59,699
Allowance for equity funds used during construction	2,219	1,572
Other, net	-90	-41
Net cash used in investing activities	-77,797	-58,168
Financing activities
Proceeds from short-term borrowings, net	2,000	11,000
Repayments of long-term debt	-128	-18
Capital contributions from parent	25,210	0
Dividends paid to parent	-14,957	-8,032
Net cash provided by financing activities	12,125	2,950
Net change in cash and cash equivalents	-295	998
Cash and cash equivalents at beginning of period	1,285	1,349
Cash and cash equivalents at end of period	990	2,347
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	-5,791	-5,827
Cash received for income taxes, net	625	5,573
Supplemental disclosure of non-cash investing transactions:
Property, plant and equipment additions in accounts payable	$14,550	$16,436

CONSOLIDATED_BALANCE_SHEETS_UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets
Cash and cash equivalents	$990	$1,285
Accounts receivable, net	65,892	60,396
Accrued unbilled revenues	43,139	53,567
Inventories	14,855	24,685
Regulatory assets	12,800	20,036
Prepaid taxes	18,247	28,628
Deferred income taxes	16,472	8,201
Prepayments and other	5,912	6,918
Total current assets	178,307	203,716
Property, plant and equipment, net	1,715,967	1,674,281
Other assets
Regulatory assets	285,328	280,693
Other investments	3,908	3,818
Other	4,649	4,612
Total other assets	293,885	289,123
Total assets	2,188,159	2,167,120
Current liabilities
Current portion of long-term debt	1,224	1,235
Short-term debt	80,000	78,000
Notes payable to affiliates	500	500
Accounts payable	33,602	61,530
Accounts payable to affiliates	21,883	26,524
Dividends payable to parent	13,315	14,957
Regulatory liabilities	14,145	16,940
Environmental liabilities	26,125	29,116
Other	20,734	19,923
Total current liabilities	211,528	248,725
Deferred credits and other liabilities
Deferred income taxes	365,798	348,180
Deferred investment tax credits	8,956	9,089
Regulatory liabilities	135,800	132,674
Environmental liabilities	86,435	78,620
Customer advances	18,449	17,623
Pension and employee benefit obligations	46,352	51,313
Other	15,872	16,151
Total deferred credits and other liabilities	677,662	653,650
Commitments and contingencies
Capitalization
Long-term debt	567,099	567,056
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at March 31, 2015 and Dec. 31, 2014, respectively	93,300	93,300
Additional paid in capital	347,486	322,276
Retained earnings	291,350	282,398
Accumulated other comprehensive loss	-266	-285
Total common stockholder’s equity	731,870	697,689
Total liabilities and equity	$2,188,159	$2,167,120

CONSOLIDATED_BALANCE_SHEETS_UN1

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
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

Managements_Opinion

Management's Opinion	3 Months Ended
	Mar. 31, 2015
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, 2015 and Dec. 31, 2014; the results of its operations, including the components of net income and comprehensive income, for the three months ended March 31, 2015 and 2014; and its cash flows for the three months ended March 31, 2015 and 2014. All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after March 31, 2015 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, 2014 balance sheet information has been derived from the audited 2014 consolidated financial statements included in the NSP-Wisconsin Annual Report on Form 10-K for the year ended Dec. 31, 2014. 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, 2014, filed with the SEC on Feb. 23, 2014. 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_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
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, 2014, 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, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Accounting Pronouncements	Accounting Pronouncements
	Recently Issued
	Revenue Recognition — In May 2014, the Financial Accounting Standards Board (FASB) issued Revenue from Contracts with Customers, Topic 606 (Accounting Standards Update (ASU) No. 2014-09), which provides a framework for the recognition of revenue, with the objective that recognized revenues properly reflect amounts an entity is entitled to receive in exchange for goods and services. This guidance, which includes additional disclosure requirements regarding revenue, cash flows and obligations related to contracts with customers, is effective for interim and annual reporting periods beginning after Dec. 15, 2016. In April 2015, the FASB tentatively decided to defer the effective date by one year, making the guidance effective for interim and annual reporting periods beginning after Dec. 15, 2017. This tentative decision will be exposed for public input in an upcoming proposed ASU with a 30-day comment period. NSP-Wisconsin is currently evaluating the impact of adopting ASU 2014-09 on its consolidated financial statements.
	Consolidation — In February 2015, the FASB issued Amendments to the Consolidation Analysis, Topic 810 (ASU No. 2015-02), which reduces the number of consolidation models and amends certain consolidation principles related to variable interest entities. This guidance will be effective for interim and annual reporting periods beginning after Dec. 15. 2015, and early adoption is permitted. NSP-Wisconsin is currently evaluating the impact of adopting ASU 2015-02 on its consolidated financial statements.
	Presentation of Debt Issuance Costs — In April 2015, the FASB issued Simplifying the Presentation of Debt Issuance Costs, Subtopic 835-30 (ASU No. 2015-03), which amends existing guidance to require the presentation of debt issuance costs on the balance sheet as a deduction from the carrying amount of the related debt, instead of an asset. This guidance will be effective for interim and annual reporting periods beginning after Dec. 15, 2015, and early adoption is permitted. Other than the prescribed reclassification of assets to an offset of debt on the consolidated balance sheets, NSP-Wisconsin does not expect the implementation of ASU 2015-03 to have a material impact on its consolidated financial statements.

Selected_Balance_Sheet_Data

Selected Balance Sheet Data	3 Months Ended
	Mar. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Data	Selected Balance Sheet Data
	(Thousands of Dollars)		March 31, 2015			Dec. 31, 2014
	Accounts receivable, net (a)
	Accounts receivable		$	71,265		$	66,217
	Less allowance for bad debts		(5,373		)	(5,821		)
			$	65,892		$	60,396
	(Thousands of Dollars)		March 31, 2015			Dec. 31, 2014
	Inventories
	Materials and supplies		$	6,661		$	6,494
	Fuel		6,958			6,654
	Natural gas		1,236			11,537
			$	14,855		$	24,685
	(Thousands of Dollars)		March 31, 2015			Dec. 31, 2014
	Property, plant and equipment, net
	Electric plant		$	2,152,862		$	2,061,669
	Natural gas plant		257,471			255,465
	Common and other property		125,153			125,938
	Construction work in progress		194,488			231,413
	Total property, plant and equipment		2,729,974			2,674,485
	Less accumulated depreciation		(1,014,007		)	(1,000,204		)
			$	1,715,967		$	1,674,281
	(a)	Accounts receivable, net includes an immaterial amount due from affiliates as of March 31, 2015 and Dec. 31, 2014, respectively.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Except to the extent noted below, Note 6 to the consolidated financial statements included in NSP-Wisconsin’s Annual Report on Form 10-K for the year ended Dec. 31, 2014 appropriately represents, in all material respects, the current status of other income tax matters, and are incorporated herein by reference.
	Federal Audit — NSP-Wisconsin is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. The statute of limitations applicable to Xcel Energy’s 2009 federal income tax return expires in March 2016. In the third quarter of 2012, the Internal Revenue Service (IRS) commenced an examination of tax years 2010 and 2011, including a 2009 carryback claim. As of March 31, 2015, the IRS had proposed an adjustment to several federal tax loss carryback claims that would result in $12 million of income tax expense for the 2009 through 2011 claims, the recently filed 2013 claim, and the anticipated claim for 2014. NSP-Wisconsin is not expected to accrue any income tax expense related to this adjustment. As of March 31, 2015, the IRS has begun the appeals process; however, the outcome and timing of a resolution is uncertain.
	State Audits — NSP-Wisconsin is a member of the Xcel Energy affiliated group that files consolidated state income tax returns. As of March 31, 2015, NSP-Wisconsin’s earliest open tax year that is subject to examination by state taxing authorities under applicable statutes of limitations is 2010. As of March 31, 2015, there were no state income tax audits in progress.
	Unrecognized Tax Benefits — The unrecognized tax benefit balance includes permanent tax positions, which if recognized would affect the annual effective tax rate (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 of cash to the taxing authority to an earlier period.
	A reconciliation of the amount of unrecognized tax benefit is as follows:
	(Millions of Dollars)	March 31, 2015			Dec. 31, 2014
	Unrecognized tax benefit — Permanent tax positions	$	0.2		$	0.1
	Unrecognized tax benefit — Temporary tax positions	2.2			2.9
	Total unrecognized tax benefit	$	2.4		$	3
	The unrecognized tax benefit amounts were reduced by the tax benefits associated with net operating loss (NOL) and tax credit carryforwards. The amounts of tax benefits associated with NOL and tax credit carryforwards are as follows:
	(Millions of Dollars)	March 31, 2015			Dec. 31, 2014
	NOL and tax credit carryforwards	$	(0.6	)	$	(0.9	)
	It is reasonably possible that NSP-Wisconsin’s amount of unrecognized tax benefits could significantly change in the next 12 months as the IRS appeals process progresses and state audits resume. As the IRS examination moves closer to completion, the change in the unrecognized tax benefit is not expected to be material.
	The payable for interest related to unrecognized tax benefits is partially offset by the interest benefit associated with NOL and tax credit carryforwards. The payables for interest related to unrecognized tax benefits at March 31, 2015 and Dec. 31, 2014 were not material. No amounts were accrued for penalties related to unrecognized tax benefits as of March 31, 2015 or Dec. 31, 2014.

Rate_Matters_Rate_Matters_Note

Rate Matters Rate Matters (Notes)	3 Months Ended
	Mar. 31, 2015
Public Utilities, General Disclosures [Abstract]
Public Utilities Disclosure [Text Block]	Rate Matters
	Pending Regulatory Proceedings — Minnesota Public Utilities Commission (MPUC)
	Nuclear Project Prudence Investigation — In 2013, NSP-Minnesota completed the Monticello life cycle management (LCM)/extended power uprate (EPU) project. The multi-year project extended the life of the facility and increased the capacity from 600 to 671 megawatts (MW). Monticello LCM/EPU project expenditures were approximately $665 million. Total capitalized costs were approximately $748 million, which includes allowance for funds used during construction (AFUDC). In 2008, project expenditures were initially estimated at approximately $320 million, excluding AFUDC.
	In 2013, the MPUC initiated an investigation to determine whether the final costs for the Monticello LCM/EPU project were prudent.
	On March 6, 2015, the MPUC voted to allow for full recovery, including a return, on approximately $415 million of the total plant costs (inclusive of AFUDC), but only allow recovery of the remaining $333 million of costs with no return on this portion of the investment over the remaining life of the plant. Further, the MPUC determined that only 50 percent of the investment was considered used and useful for 2014.  As a result of these determinations and assuming the other state commissions within the NSP System jurisdictions adopt the MPUC’s decisions, Xcel Energy recorded an estimated pre-tax loss of $129 million in the first quarter of 2015. The remaining book value of the Monticello project represents the present value of the estimated future cash flows allowed for by the MPUC. As NSP-Wisconsin shares in the costs of the Monticello plant through the Interchange Agreement with NSP-Minnesota, the MPUC decision also affects NSP-Wisconsin. NSP-Wisconsin's portion of the $129 million pre-tax loss, recorded in the first quarter of 2015, was approximately $5 million.
	Review of the final written order, which is anticipated in the second quarter of 2015, could impact these calculations. NSP-Minnesota will have the ability to file for reconsideration and any changes to the final order could impact NSP-Wisconsin as well.
	Pending Regulatory Proceedings — Michigan Public Service Commission (MPSC)
	Michigan 2015 Electric Rate Case — In October 2014, NSP-Wisconsin filed a request with the MPSC to increase rates for electric service by $900,000, or 6.1 percent. The filing was based on a 2015 forecast test year, a 10.3 percent return on equity (ROE), an equity ratio of 52.59 percent and a forecasted average rate base of approximately $35.2 million. The primary driver of the requested increase is continuing investment in transmission and distribution infrastructure. The filing also included a request for a $289,000, or 1.9 percent, step increase in 2016, to reflect the expiration in 2016 of certain credits that were used to offset the 2015 rate request. In addition to the MPSC staff, intervenors in the case include the Michigan Attorney General (AG) and the Association of Businesses Advocating Tariff Equity (ABATE), a voluntary association of large industrial businesses.
	In March 2015, NSP-Wisconsin reached a multi-year settlement with the MPSC staff and the AG. Under the agreement, NSP-Wisconsin will increase rates by $720,000 annually, or 4.9 percent, in the first year and an additional $289,000 annually, or 2.0 percent, in the second year. Rates will not increase in the third year. The new rates are based on an authorized ROE of 10.1 percent. ABATE did not sign the settlement agreement, but rather filed a statement of non-objection. On March 23, 2015, the MPSC issued an order approving the settlement agreement and authorizing new rates which were effective April 1, 2015.
	Pending Regulatory Proceedings — Federal Energy Regulatory Commission (FERC)
	Midcontinent Independent System Operator, Inc. (MISO) ROE Complaint/ROE Adder — In November 2013, a group of customers filed a complaint at the FERC against MISO transmission owners (TOs), including NSP-Minnesota and NSP-Wisconsin. The complaint argued for a reduction in the ROE in transmission formula rates in the MISO region from 12.38 percent to 9.15 percent, a prohibition on capital structures in excess of 50 percent equity, and the removal of ROE adders (including those for regional transmission organization (RTO) membership and being an independent transmission company), effective Nov. 12, 2013.
	In June 2014, the FERC issued an order in a different ROE proceeding adopting a new ROE methodology for electric utilities. The new ROE methodology requires electric utilities to use a two-step discounted cash flow analysis to estimate cost of equity that incorporates both short-term and long-term growth projections.
	In October 2014, the FERC upheld the determination of the long-term growth rate to be used together with a short-term growth rate in its new ROE methodology. The FERC separately set the ROE complaint against the MISO TOs for settlement and hearing procedures. The FERC directed parties to apply the new ROE methodology, but denied the complaints related to equity capital structures and ROE adders. The FERC established a Nov. 12, 2013 refund effective date. The settlement procedures were unsuccessful. FERC action is pending. In January 2015, the ROE complaint was set for full hearing procedures, with an administrative law judge initial decision to be issued by November 2015 and a FERC order issued no earlier than 2016.
	In November 2014, the MISO TOs filed a request for FERC approval of a 50 basis point RTO membership ROE adder, with collection deferred until resolution of the ROE complaint. In January 2015, the FERC approved the ROE adder, subject to the outcome of the ROE complaint. The total ROE, including the RTO membership adder, may not exceed the top of the discounted cash flow range under the new ROE methodology. In 2015, several intervenors sought rehearing of the commission order.
	In February 2015, a separate group of customers filed an additional complaint proposing to reduce the MISO region ROE to 8.67 percent , prior to any 50 basis point RTO adder, with a refund effective date of Feb. 12, 2015.  The FERC has to date taken no action on the second complaint.
	NSP-Minnesota recorded a current liability representing the current best estimate of a refund obligation associated with the new ROE as of March 31, 2015. The new FERC ROE methodology is estimated to reduce transmission revenue, net of expense, between $7 million and $9 million annually for the NSP System.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Except to the extent noted below and in Note 5, Notes 10 and 11 to the consolidated financial statements in NSP-Wisconsin’s Annual Report on Form 10-K for the year ended Dec. 31, 2014 appropriately represent, in all material respects, the current status of commitments and contingent liabilities, and are incorporated herein by reference. The following include commitments, contingencies and unresolved contingencies that are material to NSP-Wisconsin’s financial position.
	Guarantees
	NSP-Wisconsin provides a guarantee for payment of customer loans related to NSP-Wisconsin’s farm rewiring program. NSP-Wisconsin’s exposure under the guarantee is based upon the net liability under the agreement. The guarantee issued by NSP-Wisconsin limits its exposure to a maximum amount stated in the guarantee. The guarantee contains no recourse provisions and requires no collateral.
	The following table presents the guarantee issued and outstanding for NSP-Wisconsin:
	(Millions of Dollars)	March 31, 2015		Dec. 31, 2014
	Guarantees issued and outstanding	$	1	$	1
	Current exposure under these guarantees	0.1		0.2
	Environmental Contingencies
	Ashland Manufactured Gas Plant (MGP) Site — NSP-Wisconsin has been named a potentially responsible party (PRP) for contamination at a site in Ashland, Wis. The Ashland/Northern States Power Lakefront Superfund Site (the Ashland site) includes property owned by NSP-Wisconsin, which was a site previously operated by a predecessor company as a MGP facility (the Upper Bluff), and two other properties: an adjacent city lakeshore park area (Kreher Park), on which an unaffiliated third party previously operated a sawmill and conducted creosote treating operations; and an area of Lake Superior’s Chequamegon Bay adjoining the park (the Sediments).
	The U.S. Environmental Protection Agency (EPA) issued its Record of Decision (ROD) in 2010, which describes the preferred remedy the EPA has selected for the cleanup of the Ashland site. For the Sediments at the Ashland Site, the ROD preferred remedy is a hybrid remedy involving both dry excavation and wet conventional dredging methodologies (the Hybrid Remedy). The ROD also identifies the possibility of a wet conventional dredging only remedy for the Sediments (the Wet Dredge), contingent upon the completion of a successful Wet Dredge pilot study.
	In 2011, the EPA issued special notice letters identifying several entities, including NSP-Wisconsin, as PRPs, for future remediation at the Ashland site. As a result of settlement negotiations with NSP-Wisconsin, the EPA agreed to segment the Ashland site into separate areas. The first area (Phase I Project Area) includes soil and groundwater in Kreher Park and the Upper Bluff. The second area includes the Sediments.
	In October 2012, a settlement among the EPA, the Wisconsin Department of Natural Resources, the Bad River and Red Cliff Bands of the Lake Superior Tribe of Chippewa Indians and NSP-Wisconsin was approved by the U.S. District Court for the Western District of Wisconsin. This settlement resolves claims against NSP-Wisconsin for its alleged responsibility for the remediation of the Phase I Project Area. Under the terms of the settlement, NSP-Wisconsin agreed to perform the remediation of the Phase I Project Area, but does not admit any liability with respect to the Ashland site. Fieldwork to address the Phase I Project Area at the Ashland site began at the end of 2012 and continues. Demolition activities occurred at the Ashland site in 2013. Soil, including excavation and treatment, as well as containment wall remedies were completed in early 2015. A preliminary design for the groundwater remedy was also submitted to the EPA in April 2014 and those activities are expected to commence in 2015. The current cost estimate for the cleanup of the Phase I Project Area is approximately $57 million, of which approximately $33 million has already been spent. The settlement also resolves claims by the federal, state and tribal trustees against NSP-Wisconsin for alleged natural resource damages at the Ashland site, including both the Phase I Project Area and the Sediments.
	Negotiations are ongoing between the EPA and NSP-Wisconsin regarding who will pay for or perform the cleanup of the Sediments and what remedy will be implemented at the site to address the Sediments. It is NSP-Wisconsin’s view that the Hybrid Remedy is not safe or feasible to implement. The EPA’s ROD for the Ashland site includes estimates that the cost of the Hybrid Remedy is between $63 million and $77 million, with a potential deviation in such estimated costs of up to 50 percent higher to 30 percent lower. In November 2013, NSP-Wisconsin submitted a revised Wet Dredge pilot study work plan proposal to the EPA. In May 2014, NSP-Wisconsin entered into a final administrative order on consent for the Wet Dredge pilot study with the EPA. In early 2015, the EPA granted an extension of time to perform the pilot in 2016 so that NSP-Wisconsin can first construct a breakwater at the site to serve as a wave attenuator.
	In August 2012, NSP-Wisconsin also filed litigation against other PRPs for their share of the cleanup costs for the Ashland site. Trial for this matter commenced on April 27, 2015. Negotiations between the EPA, NSP-Wisconsin and several of the other PRPs regarding the PRPs’ fair share of the cleanup costs for the Ashland site are also ongoing. A final settlement has been reached between NSP-Wisconsin, along with the EPA, and two of the PRPs, Wisconsin Central Ltd. and Soo Line Railroad Co. (collectively, the “Railroad PRPs”) resolving claims relating to the Railroad PRPs’ share of the costs of cleanup at the Ashland site. NSP-Wisconsin also has entered a second private party settlement agreement with LE Myers Co. Under the agreements, the Railroad PRPs will contribute $10.5 million and LE Myers Co. will contribute $5.4 million to the costs of the cleanup at the Ashland site. The agreement for the Railroad PRPs along with LE Myers Co. was approved by the U.S. District Court for the Western District of Wisconsin in 2015. As discussed below, existing Public Service Commission of Wisconsin (PSCW) policy requires that any payments received from PRPs be used to reduce the amount of the cleanup costs ultimately recovered from customers.
	At March 31, 2015 and Dec. 31, 2014, NSP-Wisconsin had recorded a liability of $112.4 million and $107.6 million, respectively, for the Ashland site based upon potential remediation and design costs together with estimated outside legal and consultant costs; of which $26.0 million and $28.9 million, respectively, was considered a current liability. NSP-Wisconsin’s potential liability, the actual cost of remediation and the time frame over which the amounts may be paid are subject to change. NSP-Wisconsin also continues to work to identify and access state and federal funds to apply to the ultimate remediation cost of the entire site. Unresolved issues or factors that could result in higher or lower NSP-Wisconsin remediation costs for the Ashland site include the cleanup approach implemented for the Sediments, which party implements the cleanup, the timing of when the cleanup is implemented, potential contributions by other PRPs and whether federal or state funding may be directed to help offset remediation costs at the Ashland site.
	NSP-Wisconsin has deferred the estimated site remediation costs, as a regulatory asset, based on an expectation that the PSCW will continue to allow NSP-Wisconsin to recover payments for environmental remediation from its customers. The PSCW has consistently authorized NSP-Wisconsin rate recovery for all remediation costs incurred at the Ashland site, and has authorized recovery of MGP remediation costs by other Wisconsin utilities. Under the established PSCW policy, external MGP remediation costs are subject to deferral in the Wisconsin retail jurisdiction and are reviewed for prudence as part of the Wisconsin retail rate case process. Any payments received from insurance carriers or PRPs are recorded as a reduction of the regulatory asset. Once deferred MGP remediation costs are determined by the PSCW to be prudent, utilities are allowed to recover those deferred costs in natural gas rates, typically over a four- to six-year amortization period. The PSCW historically has not allowed utilities to recover their carrying costs on unamortized regulatory assets for MGP remediation.
	The PSCW reviewed the existing MGP cost recovery policy as it applied to the Ashland site in the context of NSP-Wisconsin's 2013 general rate case. In their final decision, dated Dec. 27, 2012, the PSCW recognized the potential magnitude of the future liability for the cleanup at the Ashland site and granted an exception to its existing policy at the request of NSP-Wisconsin. The elements of this exception include: (1) approval to begin recovery of estimated Phase 1 Project costs beginning on Jan. 1, 2013; (2) approval to amortize these estimated costs over a ten-year period; and (3) approval to apply a three percent carrying cost to the unamortized regulatory asset. In a 2014 rate case decision, the PSCW continued the cost recovery treatment with respect to the 2013 and 2014 cleanup costs for the Phase I Project Area and allowed NSP-Wisconsin to increase its 2014 amortization expense related to the cleanup by an additional $1.1 million to offset the need for a rate decrease for the natural gas utility. Cost recovery will continue at the level set in the 2014 rate case though 2015, but will be re-assessed in NSP-Wisconsin’s next natural gas rate case.
	Environmental Requirements
	Water and Waste
	Coal Ash Regulation — NSP-Wisconsin's operations are subject to federal and state laws that impose requirements for handling, storage, treatment, and disposal of solid waste.  On April 17, 2015, the EPA published a final rule regulating the management and disposal of coal combustion byproducts (coal ash) as a nonhazardous waste.  NSP-Wisconsin has ceased coal combustion at Bay Front Unit 5 and will not have any units subject to coal ash regulation. Due to the Interchange Agreement, NSP-Wisconsin may incur costs related to this rule but does not expect these to have a material impact on the results of operations, financial position or cash flows.
	Air
	Cross-State Air Pollution Rule (CSAPR) — CSAPR addresses long range transport of particulate matter and ozone by requiring reductions in sulfur dioxide (SO2) and nitrous oxide (NOx) from utilities in the eastern half of the United States, including Wisconsin, using an emissions trading program.
	In August 2012, the United States District Court of Appeals for the District of Columbia Circuit (D.C. Circuit) vacated the CSAPR and remanded it back to the EPA. The D.C. Circuit stated the EPA must continue administering the Clean Air Interstate Rule pending adoption of a valid replacement. In April 2014, the U.S. Supreme Court reversed and remanded the case to the D.C. Circuit. The Supreme Court held that the EPA’s rule design did not violate the Clean Air Act and that states had received adequate opportunity to develop their own plans. Because the D.C. Circuit overturned the CSAPR on two over-arching issues, there are many other issues the D.C. Circuit did not rule on that will now need to be considered on remand. An opinion is expected late summer 2015. In October 2014, the D.C. Circuit granted the EPA’s request to begin to implement CSAPR by imposing its 2012 compliance obligations starting in January 2015. While the litigation continues, the EPA will administer the CSAPR in 2015.
	NSP-Wisconsin can operate within its CSAPR emission allowance allocation for SO2. NSP-Wisconsin anticipates compliance with the CSAPR for NOx in 2015 through operational changes or allowance purchases. CSAPR compliance in 2015 is not expected to have a material impact on the results of operations, financial position or cash flows.
	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 a series of complex judgments about future events. Management maintains accruals for such 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 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, 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.

Borrowings_and_Other_Financing

Borrowings and Other Financing Instruments	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Borrowings and Other Financing Instruments	Borrowings and Other Financing Instruments
	Commercial Paper — NSP-Wisconsin meets its short-term liquidity requirements primarily through the issuance of commercial paper and borrowings under its credit facility. Commercial paper outstanding for NSP-Wisconsin was as follows:
	(Amounts in Millions, Except Interest Rates)		Three Months Ended March 31, 2015				Twelve Months Ended Dec. 31, 2014
	Borrowing limit		$	150			$	150
	Amount outstanding at period end		80				78
	Average amount outstanding		76				46
	Maximum amount outstanding		122				101
	Weighted average interest rate, computed on a daily basis		0.45		%		0.27		%
	Weighted average interest rate at period end		0.53				0.55
	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, 2015 and Dec. 31, 2014, 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.
	At March 31, 2015, NSP-Wisconsin had the following committed credit facility available (in millions of dollars):
	Credit Facility (a)				Drawn (b)				Available
	$	150			$	80			$	70
	(a)	This credit facility expires in October 2019.
	(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, 2015 and Dec. 31, 2014.
	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, 2015				Dec. 31, 2014
	Notes payable to affiliates		$	0.5			$	0.5
	Weighted average interest rate at period end		0.53		%		0.51		%

Fair_Value_of_Financial_Assets

Fair Value of Financial Assets and Liabilities

3 Months Ended

Mar. 31, 2015

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 certain 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. The three levels in the hierarchy are as follows:

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 the following:

Cash equivalents — The fair values of cash equivalents are generally based on cost plus accrued interest; money market funds are measured using quoted net asset values.

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.  When contractual settlements extend to periods beyond those readily observable on active exchanges or quoted by brokers, the significance of the use of less observable forecasts of long-term forward prices and volatilities 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 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, 2015, accumulated other comprehensive loss related to interest rate derivatives included $0.1 million of net losses expected to be reclassified into earnings during the next 12 months as the related hedged interest rate transactions impact earnings, including forecasted amounts for unsettled hedges, as applicable.

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.

The following table details the gross notional amounts of commodity options at March 31, 2015 and Dec. 31, 2014:

(Amounts in Thousands) (a)(b)

March 31, 2015

Dec. 31, 2014

Million British thermal units of natural gas

—

18

(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 Activities on Income and Accumulated Other Comprehensive Loss — There were immaterial pre-tax losses related to interest rate derivatives reclassified from accumulated other comprehensive loss into earnings during the three months ended March 31, 2015 and 2014.

During the three months ended March 31, 2015, changes in the fair value of natural gas commodity derivatives resulted in immaterial net losses recognized as regulatory assets and liabilities. For the three months ended March 31, 2014, changes in the fair value of natural gas commodity derivatives resulted in net gains of $0.8 million, recognized as regulatory assets and liabilities. The classification as a regulatory asset or liability is based on commission approved regulatory recovery mechanisms.

Natural gas commodity derivatives settlement gains of $1.0 million and $0.5 million were recognized for the three months ended March 31, 2015 and 2014, respectively, and were 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 ended March 31, 2015 and 2014. Therefore, no gains or losses from fair value hedges or related hedged transactions were recognized for these periods.

Consideration of Credit Risk and Concentrations — NSP-Wisconsin continuously monitors the creditworthiness of the counterparties to its interest rate derivatives and commodity derivative contracts prior to settlement, and assesses each counterparty’s ability to perform on the transactions set forth in the contracts. Given this assessment, as well as an assessment of the impact of NSP-Wisconsin’s own credit risk when determining the fair value of derivative liabilities, the impact of considering credit risk was immaterial to the fair value of unsettled commodity derivatives presented in the consolidated balance sheets.

NSP-Wisconsin employs additional credit risk control mechanisms when appropriate, such as letters of credit, parental guarantees, standardized master netting agreements and termination provisions that allow for offsetting of positive and negative exposures. Credit exposure is monitored and, when necessary, the activity with a specific counterparty is limited until credit enhancement is provided.

Recurring Fair Value Measurements — There were no recognized recurring fair value measurements at March 31, 2015. The following table presents for each of the fair value hierarchy levels, NSP-Wisconsin’s derivative assets measured at fair value on a recurring basis at Dec. 31, 2014:

Dec. 31, 2014

Fair Value

Fair Value

Counterparty

Total (b)

(Thousands of Dollars)

Level 1

Level 2

Level 3

Total

Netting (a)

Current derivative assets

Natural gas commodity

$

—

$

52

$

—

$

52

$

—

$

52

(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 Dec. 31, 2014.  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 assets balance of $6.9 million at Dec. 31, 2014, in the consolidated balance sheets.

Fair Value of Long-Term Debt

As of March 31, 2015 and Dec. 31, 2014, other financial instruments for which the carrying amount did not equal fair value were as follows:

March 31, 2015

Dec. 31, 2014

(Thousands of Dollars)

Carrying Amount

Fair Value

Carrying Amount

Fair Value

Long-term debt, including current portion

$

568,323

$

678,836

$

568,291

$

670,665

The 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. The fair value estimates are based on information available to management as of March 31, 2015 and Dec. 31, 2014, and given the observability of the inputs to these estimates, the fair values presented for long-term debt have been assigned a Level 2.

Other_Expense_Income_Net

Other (Expense) Income, Net	3 Months Ended
	Mar. 31, 2015
Other Income and Expenses [Abstract]
Other (Expense) Income, Net	Other Income, Net
	Other income, net consisted of the following:
		Three Months Ended March 31
	(Thousands of Dollars)	2015			2014
	Interest income	$	297		$	204
	Other nonoperating income	61			35
	Insurance policy expense	(106		)	(112		)
	Other nonoperating expense	(3		)	(3		)
	Other income, net	$	249		$	124

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information
	Operating results from the 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 utility, regulated natural gas utility and all other.
	•	NSP-Wisconsin’s regulated electric utility segment generates, transmits and distributes electricity primarily in portions of Wisconsin and Michigan.
	•	NSP-Wisconsin’s regulated natural gas utility segment purchases, transports, stores and distributes natural gas primarily in portions of Wisconsin and Michigan.
	•	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-Wisconsin’s reportable segments because as an integrated electric and natural gas utility, NSP-Wisconsin operates significant assets that are not dedicated to a specific business segment, and reporting assets and capital expenditures by business segment would require arbitrary and potentially misleading allocations which may not necessarily reflect the assets that would be required for the operation of the business segments on a stand-alone basis.
	To report income from operations for regulated electric and regulated natural gas utility segments, the majority of costs are directly assigned to each segment.  However, some costs, such as common depreciation, common operating and maintenance (O&M) expenses and interest expense are allocated based on cost causation allocators.  A general allocator is used for certain general and administrative expenses, including office supplies, rent, property insurance and general advertising.
	(Thousands of Dollars)		Regulated Electric			Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
	Three Months Ended March 31, 2015
	Operating revenues (a)		$	210,284		$	63,296	$	380		$	—		$	273,960
	Intersegment revenues		109			225		—			(334		)	—
	Total revenues		$	210,393		$	63,521	$	380		$	(334	)	$	273,960
	Net income (loss)		$	15,514	(b)	$	6,781	$	(28	)	$	—		$	22,267
	(Thousands of Dollars)		Regulated Electric			Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
	Three Months Ended March 31, 2014
	Operating revenues (a)		$	211,097		$	73,791	$	254		$	—		$	285,142
	Intersegment revenues		92			2,917		—			(3,009		)	—
	Total revenues		$	211,189		$	76,708	$	254		$	(3,009	)	$	285,142
	Net income		$	15,066		$	7,709	$	1,460		$	—		$	24,235
	(a)	Operating revenues include $38 million and $31 million of affiliate electric revenue for the three months ended March 31, 2015 and 2014, respectively.
	(b)	Includes a net of tax charge related to the Monticello LCM/EPU project.  See Note 5.

Benefit_Plans_and_Other_Postre

Benefit Plans and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Benefit Plans and Other Postretirement Benefits	Benefit Plans and Other Postretirement Benefits
	Components of Net Periodic Benefit Cost
		Three Months Ended March 31
		2015			2014			2015			2014
	(Thousands of Dollars)	Pension Benefits						Postretirement Health
								Care Benefits
	Service cost	$	1,190		$	1,132		$	7		$	9
	Interest cost	1,630			1,814			163			198
	Expected return on plan assets	(2,371		)	(2,411		)	(8		)	(13		)
	Amortization of prior service cost (credit)	28			28			(88		)	(88		)
	Amortization of net loss	1,701			1,654			114			167
	Net benefit cost recognized for financial reporting	$	2,178		$	2,217		$	188		$	273
	In January 2015, contributions of $90.0 million were made across four of Xcel Energy’s pension plans, of which $4.9 million was attributable to NSP-Wisconsin. Xcel Energy does not expect additional pension contributions during 2015.

Other_Comprehensive_Income

Other Comprehensive Income	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Other Comprehensive Income	Other Comprehensive Income
	Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2015 and 2014 were as follows:
			Gains and Losses on
			Cash Flow Hedges
	(Thousands of Dollars)		Three Months Ended March 31, 2015				Three Months Ended March 31, 2014
	Accumulated other comprehensive loss at Jan. 1		$	(285	)		$	(361	)
	Losses reclassified from net accumulated other comprehensive loss		19				18
	Net current period other comprehensive income		19				18
	Accumulated other comprehensive loss at March 31		$	(266	)		$	(343	)
	Reclassifications from accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014 were as follows:
			Amounts Reclassified from
			Accumulated Other
			Comprehensive Loss
	(Thousands of Dollars)		Three Months Ended March 31, 2015				Three Months Ended March 31, 2014
	Losses on cash flow hedges:
	Interest rate derivatives		$	32		(a)	$	31		(a)
	Total, pre-tax		32				31
	Tax benefit		(13		)		(13		)
	Total amounts reclassified, net of tax		$	19			$	18
	(a)	Included in interest charges.

Selected_Balance_Sheet_Data_Ta

Selected Balance Sheet Data (Tables)	3 Months Ended
	Mar. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, Net								[1]
	(Thousands of Dollars)	March 31, 2015			Dec. 31, 2014
	Accounts receivable, net (a)
	Accounts receivable	$	71,265		$	66,217
	Less allowance for bad debts	(5,373		)	(5,821		)
		$	65,892		$	60,396
Inventories
	(Thousands of Dollars)	March 31, 2015			Dec. 31, 2014
	Inventories
	Materials and supplies	$	6,661		$	6,494
	Fuel	6,958			6,654
	Natural gas	1,236			11,537
		$	14,855		$	24,685
Property, Plant and Equipment, Net
	(Thousands of Dollars)	March 31, 2015			Dec. 31, 2014
	Property, plant and equipment, net
	Electric plant	$	2,152,862		$	2,061,669
	Natural gas plant	257,471			255,465
	Common and other property	125,153			125,938
	Construction work in progress	194,488			231,413
	Total property, plant and equipment	2,729,974			2,674,485
	Less accumulated depreciation	(1,014,007		)	(1,000,204		)
		$	1,715,967		$	1,674,281
[1]	Accounts receivable, net includes an immaterial amount due from affiliates as of March 31, 2015 and Dec. 31, 2014, respectively.

Income_Taxes_Tables

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the amount of unrecognized tax benefit is as follows:
	(Millions of Dollars)	March 31, 2015			Dec. 31, 2014
	Unrecognized tax benefit — Permanent tax positions	$	0.2		$	0.1
	Unrecognized tax benefit — Temporary tax positions	2.2			2.9
	Total unrecognized tax benefit	$	2.4		$	3
Tax Benefits Associated with NOL and Tax Credit Carryforwards	The unrecognized tax benefit amounts were reduced by the tax benefits associated with net operating loss (NOL) and tax credit carryforwards. The amounts of tax benefits associated with NOL and tax credit carryforwards are as follows:
	(Millions of Dollars)	March 31, 2015			Dec. 31, 2014
	NOL and tax credit carryforwards	$	(0.6	)	$	(0.9	)

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Guarantees Issued and Outstanding	The following table presents the guarantee issued and outstanding for NSP-Wisconsin:
	(Millions of Dollars)	March 31, 2015		Dec. 31, 2014
	Guarantees issued and outstanding	$	1	$	1
	Current exposure under these guarantees	0.1		0.2

Borrowings_and_Other_Financing1

Borrowings and Other Financing Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Borrowings and Other Financing Instruments [Abstract]
Credit Facilities	At March 31, 2015, NSP-Wisconsin had the following committed credit facility available (in millions of dollars):
	Credit Facility (a)				Drawn (b)				Available
	$	150			$	80			$	70
	(a)	This credit facility expires in October 2019.
	(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, 2015				Twelve Months Ended Dec. 31, 2014
	Borrowing limit		$	150			$	150
	Amount outstanding at period end		80				78
	Average amount outstanding		76				46
	Maximum amount outstanding		122				101
	Weighted average interest rate, computed on a daily basis		0.45		%		0.27		%
	Weighted average interest rate at period end		0.53				0.55
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, 2015				Dec. 31, 2014
	Notes payable to affiliates		$	0.5			$	0.5
	Weighted average interest rate at period end		0.53		%		0.51		%

Fair_Value_of_Financial_Assets1

Fair Value of Financial Assets and Liabilities (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Gross Notional Amounts of Commodity Forwards and Options

The following table details the gross notional amounts of commodity options at March 31, 2015 and Dec. 31, 2014:

(Amounts in Thousands) (a)(b)

March 31, 2015

Dec. 31, 2014

Million British thermal units of natural gas

—

18

(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 — There were no recognized recurring fair value measurements at March 31, 2015. The following table presents for each of the fair value hierarchy levels, NSP-Wisconsin’s derivative assets measured at fair value on a recurring basis at Dec. 31, 2014:

Dec. 31, 2014

Fair Value

Fair Value

Counterparty

Total (b)

(Thousands of Dollars)

Level 1

Level 2

Level 3

Total

Netting (a)

Current derivative assets

Natural gas commodity

$

—

$

52

$

—

$

52

$

—

$

52

(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 Dec. 31, 2014.  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 assets balance of $6.9 million at Dec. 31, 2014, in the consolidated balance sheets.

Carrying Amount and Fair Value of Long-term Debt

As of March 31, 2015 and Dec. 31, 2014, other financial instruments for which the carrying amount did not equal fair value were as follows:

March 31, 2015

Dec. 31, 2014

(Thousands of Dollars)

Carrying Amount

Fair Value

Carrying Amount

Fair Value

Long-term debt, including current portion

$

568,323

$

678,836

$

568,291

$

670,665

Other_Expense_Income_Net_Table

Other (Expense) Income, Net (Tables)	3 Months Ended
	Mar. 31, 2015
Other Income and Expenses [Abstract]
Other (Expense) Income, Net	Other income, net consisted of the following:
		Three Months Ended March 31
	(Thousands of Dollars)	2015			2014
	Interest income	$	297		$	204
	Other nonoperating income	61			35
	Insurance policy expense	(106		)	(112		)
	Other nonoperating expense	(3		)	(3		)
	Other income, net	$	249		$	124

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Results by Reportable Segment
	(Thousands of Dollars)		Regulated Electric			Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
	Three Months Ended March 31, 2015
	Operating revenues (a)		$	210,284		$	63,296	$	380		$	—		$	273,960
	Intersegment revenues		109			225		—			(334		)	—
	Total revenues		$	210,393		$	63,521	$	380		$	(334	)	$	273,960
	Net income (loss)		$	15,514	(b)	$	6,781	$	(28	)	$	—		$	22,267
	(Thousands of Dollars)		Regulated Electric			Regulated Natural Gas		All Other			Reconciling Eliminations			Consolidated Total
	Three Months Ended March 31, 2014
	Operating revenues (a)		$	211,097		$	73,791	$	254		$	—		$	285,142
	Intersegment revenues		92			2,917		—			(3,009		)	—
	Total revenues		$	211,189		$	76,708	$	254		$	(3,009	)	$	285,142
	Net income		$	15,066		$	7,709	$	1,460		$	—		$	24,235
	(a)	Operating revenues include $38 million and $31 million of affiliate electric revenue for the three months ended March 31, 2015 and 2014, respectively.
	(b)	Includes a net of tax charge related to the Monticello LCM/EPU project.  See Note 5.

Benefit_Plans_and_Other_Postre1

Benefit Plans and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Components of Net Periodic Benefit Cost	Components of Net Periodic Benefit Cost
		Three Months Ended March 31
		2015			2014			2015			2014
	(Thousands of Dollars)	Pension Benefits						Postretirement Health
								Care Benefits
	Service cost	$	1,190		$	1,132		$	7		$	9
	Interest cost	1,630			1,814			163			198
	Expected return on plan assets	(2,371		)	(2,411		)	(8		)	(13		)
	Amortization of prior service cost (credit)	28			28			(88		)	(88		)
	Amortization of net loss	1,701			1,654			114			167
	Net benefit cost recognized for financial reporting	$	2,178		$	2,217		$	188		$	273

Other_Comprehensive_Income_Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Changes in Accumulated Other Comprehensive Loss, Net of Tax	Changes in accumulated other comprehensive loss, net of tax, for the three months ended March 31, 2015 and 2014 were as follows:
			Gains and Losses on
			Cash Flow Hedges
	(Thousands of Dollars)		Three Months Ended March 31, 2015				Three Months Ended March 31, 2014
	Accumulated other comprehensive loss at Jan. 1		$	(285	)		$	(361	)
	Losses reclassified from net accumulated other comprehensive loss		19				18
	Net current period other comprehensive income		19				18
	Accumulated other comprehensive loss at March 31		$	(266	)		$	(343	)
Reclassifications out of Accumulated Other Comprehensive Loss	Reclassifications from accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014 were as follows:
			Amounts Reclassified from
			Accumulated Other
			Comprehensive Loss
	(Thousands of Dollars)		Three Months Ended March 31, 2015				Three Months Ended March 31, 2014
	Losses on cash flow hedges:
	Interest rate derivatives		$	32		(a)	$	31		(a)
	Total, pre-tax		32				31
	Tax benefit		(13		)		(13		)
	Total amounts reclassified, net of tax		$	19			$	18
	(a)	Included in interest charges.

Accounting_Pronouncements_Acco

Accounting Pronouncements Accounting Pronouncements (Details)	3 Months Ended
	Mar. 31, 2015
Revenue Recognition [Abstract]
Exposure period for public comment (in days)	30 days

Selected_Balance_Sheet_Data_Ac

Selected Balance Sheet Data, Accounts Receivable (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Accounts Receivable, Net
Accounts receivable	$71,265	$66,217
Less allowance for bad debts	-5,373	-5,821
Accounts receivable, net	$65,892	$60,396

Selected_Balance_Sheet_Data_In

Selected Balance Sheet Data, Inventory (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Public Utilities, Inventory [Line Items]
Inventories	$14,855	$24,685
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	6,661	6,494
Fuel
Public Utilities, Inventory [Line Items]
Inventories	6,958	6,654
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$1,236	$11,537

Selected_Balance_Sheet_Data_Pr

Selected Balance Sheet Data, Property, Plant and Equipment (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$2,729,974	$2,674,485
Less accumulated depreciation	-1,014,007	-1,000,204
Property, plant and equipment, net	1,715,967	1,674,281
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,152,862	2,061,669
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	257,471	255,465
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	125,153	125,938
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$194,488	$231,413

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Sep. 30, 2012	Dec. 31, 2014
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit — Permanent tax positions	$200,000		$100,000
Unrecognized tax benefit — Temporary tax positions	2,200,000		2,900,000
Total unrecognized tax benefit	2,400,000		3,000,000
NOL and tax credit carryforwards	-600,000		-900,000
Amounts accrued for penalties related to unrecognized tax benefits	0		0
Internal Revenue Service (IRS)
Tax Audits [Abstract]
Earliest year subject to examination	2009
Year(s) under examination		2010 and 2011
Year of carryback claim under examination		2009
Potential Tax Adjustments	$12,000,000
State Jurisdiction (Wisconsin)
Tax Audits [Abstract]
Earliest year subject to examination	2010

Rate_Matters_Rate_Matters_Deta

Rate Matters Rate Matters (Details) (USD $)	3 Months Ended		1 Months Ended		0 Months Ended	1 Months Ended				12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Nov. 30, 2013	Jun. 30, 2014	Mar. 06, 2015	Feb. 28, 2015	Nov. 30, 2014	Mar. 31, 2015	Oct. 31, 2014	Dec. 31, 2014
Public Utilities, General Disclosures [Line Items]
Loss on Monticello life cycle management/extended power uprate project	$5,237,000	$0
FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE applicable to transmission formula rates in the MISO region, upper bound			12.38%
Public Utilities, ROE applicable to transmission formula rates in the MISO region, lower bound			9.15%
Public Utilities, maximum equity capital structure percentage allowed per the complaint			50.00%
FERC Proceeding, MISO ROE Complaint [Member] | Federal Energy Regulatory Commission (FERC)
Public Utilities, General Disclosures [Line Items]
Public Utilities, number of steps required for newly adopted ROE discounted cash flow methodology				2
NSP Minnesota [Member] | Nuclear Project Prudency Investigation [Member] [Member]
Public Utilities, General Disclosures [Line Items]
Nuclear project expenditures, Amount	665,000,000
Total capitalized nuclear project costs	748,000,000
Initial estimated nuclear project expenditures	320,000,000
NSP Minnesota [Member] | Nuclear Project Prudency Investigation [Member] [Member] | Minnesota Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Amount of recoverable investment, with return					415,000,000
Amount of recoverable investment, without a return					333,000,000
Public Utilities, Percentage of investment considered used and useful					50.00%
NSP Minnesota [Member] | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Incremental ROE basis point increase (decrease) recommended by third parties						50
Public Utilities, ROE applicable to transmission formula rates in the MISO region, recommended by third parties						8.67%
NSP Minnesota [Member] | FERC Proceeding, MISO ROE Complaint [Member] | Federal Energy Regulatory Commission (FERC)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Incremental ROE basis point increase (decrease) recommended by third parties							50
Xcel Energy Inc. | Nuclear Project Prudency Investigation [Member] [Member]
Public Utilities, General Disclosures [Line Items]
Loss on Monticello life cycle management/extended power uprate project	129,000,000
NSP-Wisconsin | Nuclear Project Prudency Investigation [Member] [Member]
Public Utilities, General Disclosures [Line Items]
Loss on Monticello life cycle management/extended power uprate project	5,000,000
NSP-Wisconsin | MPSC Proceeding - Electric Rate Case 2015 [Member] | Michigan Public Service Commission (MPSC)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount									900,000
Public Utilities, Requested Rate Increase (Decrease), Percentage									6.10%
Public Utilities, Requested Return on Equity, Percentage									10.30%
Public Utilities, Requested Equity Capital Structure, Percentage									52.59%
Public Utilities, Requested Rate Base, Amount									35,200,000
Public Utilities, Approved Return on Equity, Percentage								10.10%
NSP-Wisconsin | MPSC Proceeding - Electric Rate Case 2015, Electric Rates 2016 | Michigan Public Service Commission (MPSC)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount									289,000
Public Utilities, Requested Rate Increase (Decrease), Percentage									1.90%
Public Utilities, Approved Rate Increase (Decrease), Amount								289,000
Public Utilities, Approved Rate Increase (Decrease), Percentage								2.00%
NSP-Wisconsin | MPSC Proceeding - Electric Rate Case 2015, Electric Rates 2015 [Member] | Michigan Public Service Commission (MPSC)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount								720,000
Public Utilities, Approved Rate Increase (Decrease), Percentage								4.90%
Minimum | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Increase (decrease) in transmission revenue, net of expense, due to the new ROE methodology										-7,000,000
Minimum | NSP Minnesota [Member] | Nuclear Project Prudency Investigation [Member] [Member]
Public Utilities, General Disclosures [Line Items]
Facility generating capacity (in MW)	600
Maximum | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Increase (decrease) in transmission revenue, net of expense, due to the new ROE methodology										($9,000,000)
Maximum | NSP Minnesota [Member] | Nuclear Project Prudency Investigation [Member] [Member]
Public Utilities, General Disclosures [Line Items]
Facility generating capacity (in MW)	671

Commitments_and_Contingencies_1

Commitments and Contingencies, Guarantees and Indemnifications (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Guarantor Obligations [Line Items]
Assets Held As Collateral	$0	$0
Payment or Performance Guarantee | Customer Loans for Farm Rewiring Program
Guarantees [Abstract]
Guarantees issued and outstanding	1,000,000	1,000,000
Current exposure under these guarantees	$100,000	$200,000

Commitments_and_Contingencies_2

Commitments and Contingencies, Environmental Contingencies - Site Contingencies (Details) (USD $)	3 Months Ended	1 Months Ended
	Mar. 31, 2015	Apr. 30, 2015	Dec. 31, 2014
	Site
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Liability for estimated cost of remediating sites, current	$26,125,000		$29,116,000
Ashland MGP Site
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Number of properties included in superfund site which NSP-Wisconsin does not own	2
Liability for estimated cost of remediating sites	112,400,000		107,600,000
Liability for estimated cost of remediating sites, current	26,000,000		28,900,000
Amortization period for recovery of remediation costs in natural gas rates, low end of range (in years)	4 years
Amortization period for recovery of remediation costs in natural gas rates, high end of range (in years)	6 years
Ashland MGP Site - Phase I Project Area
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Liability for estimated cost of remediating sites	57,000,000
Estimated amount spent on Phase I Project Area cleanup	33,000,000
Approved amortization period for recovery of remediation costs in natural gas rates (in years)	10 years
Carrying cost percentage to be applied to the unamortized regulatory asset for MGP remediation (in hundredths)	3.00%
Approved increase (decrease) in amortization expense granted by a regulatory body	1,100,000
Ashland MGP Site - Sediments
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Estimated cost of remediating site, low end of range	63,000,000
Estimated cost of remediating site, high end of range	77,000,000
Potential percent of increase to the high end of the range of estimated site remediation costs (in hundredths)	50.00%
Potential percent of decrease to the low end of the range of estimated site remediation costs (in hundredths)	30.00%
NSP-Wisconsin | Ashland MGP Site
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Number of PRPs that have reached a settlement in principle	2
Site Contingency, Recovery from Third Party of Environmental Remediation Cost	10,500,000
Subsequent Event [Member] | NSP-Wisconsin | Ashland MGP Site
Ashland Manufactured Gas Plant (MGP) Site [Abstract]
Site Contingency, Recovery from Third Party of Environmental Remediation Cost		$5,400,000

Commitments_and_Contingencies_3

Commitments and Contingencies, Environmental Contingencies - Unrecorded Unconditional Purchase Obligation (Details) (Cross-State Air Pollution Rule)	Apr. 30, 2014
	Issue
Cross-State Air Pollution Rule
Environmental Requirements [Abstract]
Number of issues on which the D.C. Circuit overturned the CSAPR	2

Borrowings_and_Other_Financing2

Borrowings and Other Financing Instruments, Commercial Paper (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Amount outstanding at period end	$80,000,000	$78,000,000
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	150,000,000	150,000,000
Amount outstanding at period end	80,000,000	78,000,000
Average amount outstanding	76,000,000	46,000,000
Maximum amount outstanding	$122,000,000	$101,000,000
Weighted average interest rate, computed on a daily basis (percentage)	0.45%	0.27%
Weighted average interest rate at period end (percentage)	0.53%	0.55%

Borrowings_and_Other_Financing3

Borrowings and Other Financing Instruments, Letters of Credit (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Amount outstanding at period end	80,000	$78,000
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end	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_Financing4

Borrowings and Other Financing Instruments, Credit Facility (Details) (Credit Facility, USD $)	Mar. 31, 2015
Credit Facility
Line of Credit Facility [Line Items]
Credit Facility	$150,000,000	[1]
Drawn	80,000,000	[2]
Available	70,000,000
Direct advances on the credit facility outstanding	$0
[1]	This credit facility expires in October 2019.
[2]	Includes outstanding commercial paper.

Borrowings_and_Other_Financing5

Borrowings and Other Financing Instruments, Intercompany Borrowing Arrangement and Other Short-Term Borrowings (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Short-term Debt [Line Items]
Notes payable to affiliates	$500	$500
Notes Payable To Affiliates
Short-term Debt [Line Items]
Notes payable to affiliates	$0	$0
Weighted average interest rate at period end (percentage)	0.53%	0.51%

Fair_Value_of_Financial_Assets2

Fair Value of Financial Assets and Liabilities, Derivative Instruments (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified	MMBTU	MMBTU
Interest Rate Swap
Interest Rate Derivatives [Abstract]
Amount of accumulated other comprehensive gains (losses) related to interest rate derivatives expected to be reclassified into earnings within the next twelve months	-0.1
Natural Gas Commodity (in million British thermal units)
Gross Notional Amounts of Commodity Options [Abstract]
Derivative, Nonmonetary Notional amount	0	18,000

Fair_Value_of_Financial_Assets3

Fair Value of Financial Assets and Liabilities, Impact of Derivative Activity (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Financial Impact of Qualifying Fair Value Hedges on Earnings [Abstract]
Derivative instruments designated as fair value hedges	$0	$0
Recognized gains (losses) from fair value hedges or related hedged transactions	0	0
Other Derivative Instruments | Natural Gas Commodity
Impact of Derivative Activity on Accumulated Other Comprehensive Income (Loss) Regulatory Assets and Liabilities and Income [Abstract]
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities		800,000
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities)	$1,000,000	$500,000

Fair_Value_of_Financial_Assets4

Fair Value of Financial Assets and Liabilities, Derivative Assets and Liabilities at Fair Value (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]
Prepayments and other	$5,912	$6,918
Fair Value Measured on a Recurring Basis | Fair Value Total
Derivatives, Fair Value [Line Items]
Prepayments and other		6,900
Not Designated as Hedging Instrument | Fair Value Measured on a Recurring Basis | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		52
Not Designated as Hedging Instrument | Fair Value Measured on a Recurring Basis | Level 1 | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0
Not Designated as Hedging Instrument | Fair Value Measured on a Recurring Basis | Level 2 | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		52
Not Designated as Hedging Instrument | Fair Value Measured on a Recurring Basis | Level 3 | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0
Not Designated as Hedging Instrument | Fair Value Measured on a Recurring Basis | Fair Value Total | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		52
Not Designated as Hedging Instrument | Fair Value Measured on a Recurring Basis | Netting | Other Current Assets | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		$0

Fair_Value_of_Financial_Assets5

Fair Value of Financial Assets and Liabilities, Fair Value of Long-Term Debt (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Carrying Amount
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, including current portion	$568,323	$568,291
Fair Value
Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, including current portion	$678,836	$670,665

Other_Expense_Income_Net_Detai

Other (Expense) Income, Net (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Other Income and Expenses [Abstract]
Interest income	$297	$204
Other nonoperating income	61	35
Insurance policy expense	-106	-112
Other nonoperating expense	-3	-3
Other income, net	$249	$124

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Segment Reporting Information [Line Items]
Operating revenues	$273,960,000		$285,142,000
Net income (loss)	22,267,000		24,235,000
Affiliate electric revenue	38,000,000		31,000,000
Regulated Electric
Segment Reporting Information [Line Items]
Operating revenues	210,393,000		211,189,000
Net income (loss)	15,514,000	[1]	15,066,000
Regulated Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	63,521,000		76,708,000
Net income (loss)	6,781,000		7,709,000
All Other
Segment Reporting Information [Line Items]
Operating revenues	380,000		254,000
Net income (loss)	-28,000		1,460,000
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	273,960,000	[2]	285,142,000	[2]
Operating Segments | Regulated Electric
Segment Reporting Information [Line Items]
Operating revenues	210,284,000	[2]	211,097,000	[2]
Operating Segments | Regulated Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	63,296,000		73,791,000
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues	380,000		254,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	-334,000		-3,009,000
Intersegment Eliminations | Regulated Electric
Segment Reporting Information [Line Items]
Operating revenues	109,000		92,000
Intersegment Eliminations | Regulated Natural Gas
Segment Reporting Information [Line Items]
Operating revenues	225,000		2,917,000
Intersegment Eliminations | All Other
Segment Reporting Information [Line Items]
Operating revenues	$0		$0
[1]	Includes a net of tax charge related to the Monticello LCM/EPU project. See Note 5.
[2]	Operating revenues include $38 million and $31 million of affiliate electric revenue for the three months ended March 31, 2015 and 2014, respectively.

Benefit_Plans_and_Other_Postre2

Benefit Plans and Other Postretirement Benefits (Details) (USD $)	1 Months Ended	3 Months Ended
	Jan. 31, 2015	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$1,190,000	$1,132,000
Interest cost		1,630,000	1,814,000
Expected return on plan assets		-2,371,000	-2,411,000
Amortization of prior service cost (credit)		28,000	28,000
Amortization of net loss		1,701,000	1,654,000
Net benefit cost recognized for financial reporting		2,178,000	2,217,000
Total contributions to the pension plans during the period	4,900,000
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		7,000	9,000
Interest cost		163,000	198,000
Expected return on plan assets		-8,000	-13,000
Amortization of prior service cost (credit)		-88,000	-88,000
Amortization of net loss		114,000	167,000
Net benefit cost recognized for financial reporting		188,000	273,000
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Total contributions to the pension plans during the period	$90,000,000
Number of Xcel Energy's pension plans to which contributions were made	4

Other_Comprehensive_Income_Det

Other Comprehensive Income (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	($285)
Accumulated other comprehensive loss at end of period	-266
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total, pre-tax	-35,331		-38,158
Tax benefit	13,064		13,923
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	-285		-361
Losses reclassified from net accumulated other comprehensive loss	19		18
Net current period other comprehensive income	19		18
Accumulated other comprehensive loss at end of period	-266		-343
Gains and Losses on Cash Flow Hedges | Amounts Reclassified from Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total, pre-tax	32		31
Tax benefit	-13		-13
Total, net of tax	19		18
Gains and Losses on Cash Flow Hedges | Interest Rate Derivatives | Amounts Reclassified from Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest charges	$32	[1]	$31	[1]
[1]	Included in interest charges.