XML 21 R37.htm IDEA: XBRL DOCUMENT v2.4.1.9
Commitments and Contingencies, Purchased Power Agreements (Details) (Independent Power Producing Entities)
 3 Months Ended
Mar. 31, 2015
MW
Dec. 31, 2014
MW
Independent Power Producing Entities
    
Purchased Power Agreements [Abstract]    
Generating capacity under long term purchased power agreements 1,802psco_GeneratingCapacityUnderLongTermPurchasedPowerAgreements
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityNotPrimaryBeneficiaryAggregatedDisclosureMember		 1,802psco_GeneratingCapacityUnderLongTermPurchasedPowerAgreements
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityNotPrimaryBeneficiaryAggregatedDisclosureMember
Purchase Power Agreement Duration, Maximum (year) 2032