Borrowings and Other Financing Instruments Borrowings and Other Financing Instruments, Amended Credit Agreements (Details) - Credit Facilities - USD ($)		9 Months Ended
		Sep. 30, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Long-term Line of Credit		$ 0	$ 0
Borrowing limit	[1]	$ 2,750,000,000.00
Original Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Maturity Date		Oct. 31, 2019
Amended Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Maturity Date		Jun. 30, 2021
Xcel Energy Inc.
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Borrowing limit	[1]	$ 1,000,000,000
Maturity Date		Jun. 30, 2021
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
Xcel Energy Inc. | Original Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.875%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.75%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.075%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.275%
Xcel Energy Inc. | Amended Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.75%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.50%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.06%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.225%
PSCo
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Borrowing limit	[1]	$ 700,000,000
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
PSCo | Original Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.875%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.75%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.075%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.275%
PSCo | Amended Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.75%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.50%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.06%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.225%
NSP-Minnesota
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Borrowing limit	[1]	$ 500,000,000
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
NSP-Minnesota | Original Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.875%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.75%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.075%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.275%
NSP-Minnesota | Amended Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.75%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.50%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.06%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.225%
SPS
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Borrowing limit	[1]	$ 400,000,000
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
SPS | Original Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.875%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.75%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.075%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.275%
SPS | Amended Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.75%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.50%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.06%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.225%
NSP-Wisconsin
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Borrowing limit	[1]	$ 150,000,000
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
NSP-Wisconsin | Original Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.875%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.75%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.075%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.275%
NSP-Wisconsin | Amended Terms and Conditions [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Minimum Borrowing Margin Based On Long Term Credit Ratings		0.75%
Line Of Credit Facility Maximum Borrowing Margin Based On Long Term Credit Ratings		1.50%
Line Of Credit Facility Minimum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.06%
Line Of Credit Facility Maximum Commitment Fees Calculated On Unused Portion Of Lines Of Credit		0.225%

[1] These credit facilities expire in June 2021.