Management's Opinion	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Opinion	In the opinion of management, the accompanying unaudited financial statements contain all adjustments necessary to present fairly, in accordance with U.S. GAAP, the financial position of SPS as of June 30, 2020 and Dec. 31, 2019; the results of its operations, including the components of net income and comprehensive income, and changes in stockholder’s equity for the three and six months ended June 30, 2020 and 2019; and its cash flows for the six months ended June 30, 2020 and 2019. All adjustments are of a normal, recurring nature, except as otherwise disclosed. Management has also evaluated the impact of events occurring after June 30, 2020 up to the date of issuance of these financial statements. These statements contain all necessary adjustments and disclosures resulting from that evaluation. The Dec. 31, 2019 balance sheet information has been derived from the audited 2019 financial statements included in the SPS Annual Report on Form 10-K for the year ended Dec. 31, 2019. These notes to the 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 financial statements and notes thereto, included in the SPS Annual Report on Form 10-K for the year ended Dec. 31, 2019, filed with the SEC on Feb. 21, 2020. Due to the seasonality of SPS’ electric sales, interim results are not necessarily an appropriate base from which to project annual results.