Fair Value of Financial Assets and Liabilities, Changes in Level 3 Commodity Derivatives (Details) (Commodity Derivatives, Net [Member], USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Commodity Derivatives, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers into Level 3	$ 0	$ 0
Transfers out of Level 3	$ 0	$ 0

Transfers out of net assets and liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

No definition available.

Name:	psco_FairValueMeasurementWithUnobservableInputsReconciliationAssetLiabilityNetTransfersOutOfLevel3
Namespace Prefix:	psco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration