Commitments and Contingencies, Legal Contingencies (Details) (USD $)	Sep. 30, 2012 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]	Sep. 30, 2012 Comer vs. Xcel Energy Inc. et al. [Member]	May 31, 2011 Comer vs. Xcel Energy Inc. et al. [Member]	Sep. 30, 2012 Exelon Wind Complaint [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
Number of main areas of dispute					2
Number of wind facilities					12