Commitments and Contingent Liabilities, Legal Contingencies (Details) (USD $) In Millions, unless otherwise specified									1 Months Ended
	Dec. 31, 2011 Native Village of Kivalina vs. Xcel Energy Inc. et al. [Member]	Feb. 28, 2008 Native Village of Kivalina vs. Xcel Energy Inc. et al. [Member]	Dec. 31, 2011 Comer vs. Xcel Energy Inc. et al. [Member]	May 27, 2011 Comer vs. Xcel Energy Inc. et al. [Member]	Dec. 31, 2011 Merricourt Wind Project Litigation [Member]	May 05, 2011 Merricourt Wind Project Litigation [Member]	Mar. 31, 2011 Merricourt Wind Project Litigation [Member] MW	Jul. 31, 2004 State of Connecticut vs. Xcel Energy Inc. et al. [Member]	Jul. 31, 2009 Stone & Webster, Inc. vs. PSCo [Member]	Aug. 31, 2009 Stone & Webster, Inc. vs. PSCo [Member]
Environmental Litigation [Abstract]
Number of states in which the attorneys general filed lawsuits in U.S. District Court in the Southern District of New York to force reductions in CO2 emissions								8
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
Estimated cost of relocating the village of Kivalina, high end of range	400
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
Employment, Tort and Commercial Litigation [Abstract]
Alleged guarantee of future profit									10
Damages claimed by plaintiff									144
Damages sought by the entity against the plaintiff										82
Generating capacity (in MW)							150
Merricourt deposit							101
Minimum amount of damages claimed by plaintiff						$ 240