Borrowings and Other Financing Instruments, Long-Term Borrowings and Other Financing Instruments (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
2016	$ 657,000,000
2017	638,000,000
2018	1,206,000,000
2019	406,000,000
2020	1,257,000,000
Xcel Energy Inc. \| Senior Unsecured Notes \| Series Due June 1, 2017
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 250,000,000
Interest rate, stated percentage (in hundredths)	1.20%
Maturity date	Jun. 01, 2017
Xcel Energy Inc. \| Senior Unsecured Notes \| Series Due June 1, 2025
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 250,000,000
Interest rate, stated percentage (in hundredths)	3.30%
Maturity date	Jun. 01, 2025
PSCo \| First Mortgage Bonds \| Series Due May 15, 2025
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 250,000,000
Interest rate, stated percentage (in hundredths)	2.90%
Maturity date	May 15, 2025
PSCo \| First Mortgage Bonds \| Series Due March 15, 2044
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount		$ 300,000,000
Interest rate, stated percentage (in hundredths)	4.30%	4.30%
Maturity date	Mar. 15, 2044	Mar. 15, 2044
NSP-Minnesota \| First Mortgage Bonds \| Series Due May 15, 2044
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount		$ 300,000,000
Interest rate, stated percentage (in hundredths)	4.125%	4.125%
Maturity date	May 15, 2044	May 15, 2044
NSP-Minnesota \| First Mortgage Bonds \| Series Due Aug. 15, 2020
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 300,000,000
Interest rate, stated percentage (in hundredths)	2.20%
Maturity date	Aug. 15, 2020
NSP-Minnesota \| First Mortgage Bonds \| Series Due Aug. 15, 2045
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 300,000,000
Interest rate, stated percentage (in hundredths)	4.00%
Maturity date	Aug. 15, 2045
SPS \| First Mortgage Bonds \| Series No. 3 Due June 15, 2024
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount		$ 150,000,000
Interest rate, stated percentage (in hundredths)		3.30%
Maturity date		Jun. 15, 2024
SPS \| First Mortgage Bonds \| Issued Collateral on Series G Senior Note Due Dec. 1, 2018
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount		$ 250,000,000
Interest rate, stated percentage (in hundredths)		8.75%
Maturity date		Dec. 01, 2018
SPS \| First Mortgage Bonds \| Series Due June 15, 2024
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 200,000,000
Interest rate, stated percentage (in hundredths)	3.30%	3.30%
Maturity date	Jun. 15, 2024	Jun. 15, 2024
SPS \| Senior Unsecured Notes \| Previously Issued Series G Senior Note Due Dec. 1, 2018
Long-Term Borrowings and Other Financing Instruments [Abstract]
Interest rate, stated percentage (in hundredths)	8.75%	8.75%
Maturity date	Dec. 01, 2018	Dec. 01, 2018
NSP-Wisconsin \| First Mortgage Bonds \| Series Due June 15, 2024
Long-Term Borrowings and Other Financing Instruments [Abstract]
Face amount	$ 100,000,000	$ 100,000,000
Interest rate, stated percentage (in hundredths)	3.30%	3.30%
Maturity date	Jun. 15, 2024	Jun. 15, 2024

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

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