Benefit Plans and Other Postretirement Benefits, Pension Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) (Pension Plans, USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2014	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation at Dec. 31		$ 153,894,000		$ 169,939,000
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	163,930,000	179,995,000		159,766,000
Service cost		5,682,000		4,568,000		4,271,000
Interest cost		6,924,000		7,765,000		8,031,000
Plan amendments		(1,109,000)		216,000
Actuarial (gain) loss		(11,097,000)		21,083,000
Benefit payments		(16,465,000)		(13,403,000)
Obligation at Dec. 31		163,930,000		179,995,000		159,766,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	136,935,000	136,546,000		121,348,000
Actual return (loss) on plan assets		5,525,000		16,079,000
Employer contributions		11,329,000		12,522,000
Benefit payments		(16,465,000)		(13,403,000)
Fair value of plan assets at Dec. 31		136,935,000		136,546,000		121,348,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status		(26,995,000)	[1]	(43,449,000)	[1]
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss		84,773,000		99,338,000
Prior service (credit) cost		778,000		2,290,000
Total		85,551,000		101,628,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Current regulatory assets		7,631,000		6,895,000
Noncurrent regulatory assets		77,920,000		94,733,000
Total		85,551,000		101,628,000
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Measurement date		12/31/2013		12/31/2012
Discount rate for year-end valuation (in hundredths)		4.75%		4.00%
Expected average long-term increase in compensation level (in hundredths)		3.75%		3.75%
Mortality table		RP 2000		RP 2000
Cash Flows [Abstract]
Total contributions to Xcel Energy's pension plans during the period	8,000,000	11,300,000		12,500,000		6,400,000
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		5,682,000		4,568,000		4,271,000
Interest cost		6,924,000		7,765,000		8,031,000
Expected return on plan assets		(9,995,000)		(10,489,000)		(11,484,000)
Amortization of prior service cost (credit)		417,000		1,771,000		1,895,000
Amortization of net loss		7,924,000		6,004,000		4,070,000
Net periodic benefit cost		10,952,000		9,619,000		6,783,000
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (in hundredths)		4.00%		5.00%		5.50%
Expected average long-term increase in compensation level (in hundredths)		3.75%		4.00%		4.00%
Expected average long-term rate of return on assets (in hundredths)		7.25%		7.50%		8.00%
Allocated costs for pension plans sponsored by Xcel Energy Inc.		2,200,000		1,800,000		1,300,000
Expected average long-term rate of return on assets for next fiscal year (in hundredths)		7.25%
Number of years fair market value of plan assets is adjusted using calculated value method (in years)		5 years
Annual adjustment rate used in calculated value method (in hundredths)		20.00%
Xcel Energy Inc.
Cash Flows [Abstract]
Total contributions to Xcel Energy's pension plans during the period	$ 130,000,000	$ 192,400,000		$ 198,100,000		$ 137,300,000
Number of pension plans to which contributions were made	3	4		4		3

[1] Amounts are recognized in noncurrent liabilities on NSP-Wisconsin’s consolidated balance sheets.