Commitments and Contingencies, Legal Contingencies (Details) (USD $)	3 Months Ended						14 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 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	Mar. 31, 2013 Comer vs. Xcel Energy Inc. et al. [Member]	May 31, 2011 Comer vs. Xcel Energy Inc. et al. [Member] Counterparty	Jun. 30, 2001 Pacific Northwest FERC Refund Proceeding [Member]	Mar. 31, 2013 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
Estimated cost of relocating the village of Kivalina, low end of range			$ 95,000,000
Estimated cost of relocating the village of Kivalina, high end of range			400,000,000
Accrual for legal contingency			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
Minimum amount of damages claimed by plaintiff								34,000,000
Sales to the City of Seattle	1,117,457,000	1,076,052,000					50,000,000
Estimated City of Seattle's claim for refunds not including interest								$ 28,000,000