Commitments and Contingencies, Environmental Contingencies - Unrecorded Unconditional Purchase Obligation (Details) (PSCo, Regional Haze Rules)	Dec. 31, 2010 Kiln Boiler Group
PSCo \| Regional Haze Rules
Environmental Requirements [Abstract]
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:	xel_NumberOfEnvironmentalGroupsWhoPetitionedTheU.S.DepartmentOfTheInterior
Namespace Prefix:	xel_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant