Commitments and Contingencies, Legal Contingencies (Details) (USD $)	Sep. 30, 2013	May 31, 2011 Counterparty
Legal Contingencies [Abstract]
Accrual for legal contingency	$ 0
Comer vs. Xcel Energy Inc. et al. [Member]
Legal Contingencies [Abstract]
Accrual for legal contingency	$ 0
Minimum number of utility, oil, chemical and coal companies against which a lawsuit was filed in U.S. District Court in Mississippi		85