Commitments and Contingencies, Legal Contingencies (Details) (USD $)	3 Months Ended		6 Months Ended						6 Months Ended					1 Months Ended									13 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Native Village of Kivalina vs. Xcel Energy Inc. et al. [Member]	Feb. 29, 2008 Native Village of Kivalina vs. Xcel Energy Inc. et al. [Member] Counterparty	Jun. 30, 2013 Comer vs. Xcel Energy Inc. et al. [Member]	May 31, 2011 Comer vs. Xcel Energy Inc. et al. [Member] Counterparty	Jun. 30, 2013 Pacific Northwest FERC Refund Proceeding [Member] Factor	Jun. 30, 2013 NSP-Minnesota Merricourt Wind Project Litigation [Member]	May 31, 2011 NSP-Minnesota Merricourt Wind Project Litigation [Member]	Apr. 30, 2011 NSP-Minnesota Merricourt Wind Project Litigation [Member] MW	Mar. 31, 2011 NSP-Minnesota Merricourt Wind Project Litigation [Member]	Dec. 31, 2012 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Oct. 31, 2012 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Mar. 31, 2012 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Aug. 31, 2011 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Jul. 31, 2011 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Sep. 30, 2007 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Jun. 30, 2013 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	May 15, 2013 NSP-Minnesota Nuclear Waste Disposal Litigation [Member]	Jun. 30, 2013 SPS Exelon Wind Complaint [Member] Site Dispute	Jun. 30, 2001 PSCo Pacific Northwest FERC Refund Proceeding [Member]	Jun. 30, 2013 PSCo Pacific Northwest FERC Refund Proceeding [Member]
Legal Contingencies [Abstract]
Number of other entities against which the native village of Kivalina has filed a lawsuit						23
Accrual for legal contingency					$ 0		$ 0			$ 0												$ 0		$ 0
Minimum number of utility, oil, chemical and coal companies against which a lawsuit was filed in U.S. District Court in Mississippi								85
Generating capacity (in MW)												150
Merricourt deposit													101,000,000
Minimum amount of damages claimed by plaintiff											240,000,000													34,000,000
Number of main areas of dispute																						2
Number of wind facilities																						12
Sales to the City of Seattle	2,578,913,000	2,274,668,000	5,361,762,000	4,852,747,000																			50,000,000
Estimated City of Seattle's claim for refunds not including interest																								28,000,000
Number of factors considered in assessment									2
Damages awarded																			116,500,000
Storage costs for spent nuclear fuel																				100,000,000
Cash payment received under settlement agreement															20,700,000	18,600,000	100,000,000	100,000,000
Claim submitted for storage costs for spent nuclear fuel																					42,800,000
Minnesota retail portion of the Department of Energy settlement required to be placed into the nuclear decommissioning fund														$ 15,300,000