Borrowings and Other Financing Instruments Borrowings and Other Financing Instruments, Amended Credit Agreements (Details) (Credit Facilities, Subsequent Event, USD $) In Millions, unless otherwise specified	1 Months Ended
	Oct. 31, 2014
Amended Credit Agreements [Line Items]
Amended Credit Facility, Maximum Borrowing Limit	$ 2,750
Original Credit Facility, Maximum Borrowing Limit	2,450
Xcel Energy Inc.
Amended Credit Agreements [Line Items]
Amended Credit Agreements, Commencement Date	Oct. 14, 2014
Amended Term (in years)	5 years
Amended Credit Facility, Maximum Borrowing Limit	1,000
Original Credit Facility, Maximum Borrowing Limit	800
Number Of Additional Periods The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval	2
Term Of Each Additional Period The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval (in years)	1 year
Xcel Energy Inc. | Minimum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.075%
Xcel Energy Inc. | Maximum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.275%
Xcel Energy Inc. | Eurodollar | Minimum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	0.875%
Xcel Energy Inc. | Eurodollar | Maximum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	1.75%
NSP-Minnesota
Amended Credit Agreements [Line Items]
Amended Credit Agreements, Commencement Date	Oct. 14, 2014
Amended Term (in years)	5 years
Number Of Additional Periods The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval	2
Term Of Each Additional Period The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval (in years)	1 year
NSP-Minnesota | Minimum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.075%
NSP-Minnesota | Maximum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.275%
NSP-Minnesota | Eurodollar | Minimum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	0.875%
NSP-Minnesota | Eurodollar | Maximum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	1.75%
NSP-Wisconsin
Amended Credit Agreements [Line Items]
Amended Credit Agreements, Commencement Date	Oct. 14, 2014
Amended Term (in years)	5 years
Number Of Additional Periods The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval	1
Term Of Each Additional Period The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval (in years)	1 year
NSP-Wisconsin | Minimum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.075%
NSP-Wisconsin | Maximum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.275%
NSP-Wisconsin | Eurodollar | Minimum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	0.875%
NSP-Wisconsin | Eurodollar | Maximum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	1.75%
PSCo
Amended Credit Agreements [Line Items]
Amended Credit Agreements, Commencement Date	Oct. 14, 2014
Amended Term (in years)	5 years
Number Of Additional Periods The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval	2
Term Of Each Additional Period The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval (in years)	1 year
PSCo | Minimum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.075%
PSCo | Maximum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.275%
PSCo | Eurodollar | Minimum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	0.875%
PSCo | Eurodollar | Maximum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	1.75%
SPS
Amended Credit Agreements [Line Items]
Amended Credit Agreements, Commencement Date	Oct. 14, 2014
Amended Term (in years)	5 years
Amended Credit Facility, Maximum Borrowing Limit	400
Original Credit Facility, Maximum Borrowing Limit	$ 300
Number Of Additional Periods The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval	2
Term Of Each Additional Period The Revolving Termination Date Can Be Extended, Subject To Majority Bank Group Approval (in years)	1 year
SPS | Minimum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.075%
SPS | Maximum
Amended Credit Agreements [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.275%
SPS | Eurodollar | Minimum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	0.875%
SPS | Eurodollar | Maximum
Amended Credit Agreements [Line Items]
Borrowing Margin Based On Long-Term Credit Ratings (percentage)	1.75%