Commitments and Contingencies, Purchased Power Agreements (Details) - Independent Power Producing Entities - MW	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Purchased Power Agreements [Abstract]
Generating capacity under long term purchased power agreements	1,802	1,802
Purchase Power Agreement Duration, Maximum (year)	2032	2032

The maximum duration of purchase power agreements currently under contract (year).

No definition available.

Name:	psco_PurchasePowerAgreementDurationMaximum
Namespace Prefix:	psco_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration