Segments Of Business (Products And Services) (Details)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Products and services	100.00%	100.00%	100.00%
Utility electric operations [Member]
Segment Reporting Information [Line Items]
Products and services	84.00%	82.00%	82.00%
Utility gas operations [Member]
Segment Reporting Information [Line Items]
Products and services	13.00%	15.00%	15.00%
Utility other [Member]
Segment Reporting Information [Line Items]
Products and services	2.00%	2.00%	2.00%
Other [Member]
Segment Reporting Information [Line Items]
Products and services	1.00%	1.00%	1.00%