Commitments and Contingencies, Purchased Power Agreements (Details)	Mar. 31, 2013 MW	Dec. 31, 2012 MW
Purchased Power Agreements [Abstract]
Generating capacity (in MW)	1,433	1,433

Generating capacity under long-term purchased power agreements.

No definition available.

Name:	psco_GeneratingCapacityUnderLongTermPurchasedPowerAgreements
Namespace Prefix:	psco_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant