Commitments and Contingencies, Legal Contingencies (Details) (USD $)							3 Months Ended
	Jun. 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]	Jun. 30, 2012 Comer vs. Xcel Energy Inc. et al. [Member]	May 31, 2011 Comer vs. Xcel Energy Inc. et al. [Member]	Jun. 30, 2012 Exelon Wind (formerly John Deere Wind) Complaint [Member]	Jun. 30, 2012 Exelon Wind Complaint - State Lawsuit Regarding Disputed Energy Payments [Member]	Jun. 20, 2012 Exelon Wind Complaint - State Lawsuit Regarding Wind Facility Registration with Southwest Power Pool (SPP) [Member]	Jun. 30, 2012 NSP-Minnesota [Member] Merricourt Wind Project Litigation [Member]	May 31, 2011 NSP-Minnesota [Member] Merricourt Wind Project Litigation [Member]	Apr. 30, 2011 NSP-Minnesota [Member] Merricourt Wind Project Litigation [Member] MW	Mar. 31, 2011 NSP-Minnesota [Member] Merricourt Wind Project Litigation [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		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
Number of lawsuits filed related to disputed energy payments					4
Accrual for legal contingency							$ 2,000,000