Schedule I, Condensed Financial Statements of Xcel Energy Inc, Notes to Condensed Financial Statements (Details) - Xcel Energy Inc. - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	$ 315,866,000	$ 315,866,000	$ 270,921,000
Accounts Payable	0	0	0
Dividends [Abstract]
Cash dividends paid to Xcel Energy by subsidiaries		784,000,000	857,000,000	$ 606,000,000
Money Pool [Abstract]
Lending limit	250,000,000	250,000,000	250,000,000	250,000,000
Loan outstanding at period end	0	0	16,000,000	72,000,000
Average loan outstanding	38,000,000	27,000,000	25,000,000	88,000,000
Maximum loan outstanding	$ 99,000,000	$ 141,000,000	$ 250,000,000	$ 243,000,000
Weighted average interest rate, computed on a daily basis (percentage)	0.38%	0.42%	0.22%	0.30%
Weighted average interest rate at period end (percentage)			0.45%	0.25%
Money pool interest income	$ 0	$ 100,000	$ 100,000	$ 300,000
NSP-Minnesota
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	58,952,000	58,952,000	79,390,000
Accounts Payable	0	0	0
NSP-Wisconsin
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	17,391,000	17,391,000	20,117,000
Accounts Payable	0	0	0
PSCo
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	114,524,000	114,524,000	38,646,000
Accounts Payable	0	0	0
SPS
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	21,357,000	21,357,000	28,062,000
Accounts Payable	0	0	0
Xcel Energy Services Inc.
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	73,054,000	73,054,000	75,954,000
Accounts Payable	0	0	0
Xcel Energy Ventures Inc.
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	20,003,000	20,003,000	20,082,000
Accounts Payable	0	0	0
Other Subsidiaries
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	10,585,000	10,585,000	8,670,000
Accounts Payable	$ 0	$ 0	$ 0