Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Funded Status of Plans at Dec. 31 [Abstract]
Noncurrent liabilities	$ (63,643,000)	$ (60,328,000)
Postretirement Benefit Plan [Member]
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	22,127,000	20,753,000
Service cost	20,000	17,000	15,000
Interest cost	1,075,000	1,144,000	1,234,000
Medicare subsidy reimbursements	189,000	180,000
Early Retiree Reinsurance Program proceeds shared with retirees	0	298,000
Plan amendments	(3,440,000)	0
Plan participants' contributions	893,000	1,059,000
Actuarial loss	1,486,000	2,425,000
Benefit payments	(2,918,000)	(3,749,000)
Obligation at Dec. 31	19,432,000	22,127,000	20,753,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	746,000	992,000
Actual return on plan assets	3,000	(1,000)
Plan participants' contributions	893,000	1,059,000
Employer contributions	1,923,000	2,445,000
Benefit payments	(2,918,000)	(3,749,000)
Fair value of plan assets at Dec. 31	647,000	746,000	992,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status	(18,785,000)	(21,381,000)
Current liabilities	(943,000)	(1,281,000)
Noncurrent liabilities	(17,842,000)	(20,100,000)
Net postretirement amounts recognized on consolidated balance sheets	(18,785,000)	(21,381,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss	13,730,000	12,683,000
Prior service credit	(3,538,000)	(112,000)
Transition obligation	1,000	172,000
Total	10,193,000	12,743,000
Amounts Related to the Funded Status of the Plans Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Current regulatory assets	433,000	697,000
Noncurrent regulatory assets	9,760,000	12,046,000
Total	10,193,000	12,743,000
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Measurement date	Dec. 31, 2012	Dec. 31, 2011
Discount rate for year-end valuation (in hundredths)	4.10%	5.00%
Mortality table	RP 2000	RP 2000
Health care costs trend rate - initial (in hundredths)	7.50%	6.31%
Ultimate health care trend assumption rate (in hundredths)	4.50%	5.00%
Period until ultimate trend rate is reached (in years)	7 years
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
1-percent increase in APBO	1,712,000
1-percent decrease in APBO	(1,376,000)
1-percent increase in service and interest components	126,000
1-percent decrease in service and interest components	(102,000)
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	1,900,000	2,400,000
Expected contribution to postretirement health care plans during 2013	1,600,000
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	20,000	17,000	15,000
Interest cost	1,075,000	1,144,000	1,234,000
Expected return on plan assets	(50,000)	(74,000)	(103,000)
Amortization of transition obligation	171,000	171,000	171,000
Amortization of prior service cost	(14,000)	(14,000)	(14,000)
Amortization of net loss	486,000	366,000	342,000
Net periodic benefit cost	1,688,000	1,610,000	1,645,000
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (in hundredths)	5.00%	5.50%	6.00%
Expected average long-term rate of return on assets (in hundredths)	6.75%	7.50%	7.50%
Xcel Energy Inc. [Member] | Postretirement Benefit Plan [Member]
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	47,100,000	49,000,000
Expected contribution to postretirement health care plans during 2013	$ 21,800,000