Commitments and Contingencies, Environmental Contingencies (Details) (Regional Haze Rules [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2010 Boiler Kiln Group	Mar. 31, 2013 Capital Commitments [Member]
Environmental Requirements [Abstract]
Liability for estimated cost to comply with regulation		$ 340.9
Number of environmental groups who petitioned the U.S. Department of the Interior	2
Number of coal-fired boilers in Colorado	12
Number of coal-fired cement kilns in Colorado	1

The number of environmental groups petitioning the U.S. Department of the Interior to certify that the coal-fired boilers and the coal-fired cement kiln in Colorado are contributing to visibility problems in Rocky Mountain National Park.

No definition available.

Name:	psco_NumberOfEnvironmentalGroupsWhoPetitionedUsDepartmentOfInterior
Namespace Prefix:	psco_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant