Accounting Pronouncements (Details)	Mar. 31, 2012
Accounting Pronouncements [Abstract]
Number of statements offered in specific presentation option in order to comply with new requirements pertaining to total comprehensive income	2

The number of statements offered in a specific presentation option in order to comply with the new requirements pertaining to total comprehensive income.

No definition available.

Name:	xel_NumberOfStatementsOfferedInSpecificPresentationOptionInOrderToComplyWithNewRequirementsPertainingToTotalComprehensiveIncome
Namespace Prefix:	xel_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant