Operating Revenue (Operating Revenue) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Regulated and Unregulated Operating Revenue [Abstract]
Income (loss) from discontinued operations, net of tax	$ 0	[1]	$ (155)	[1]	$ 26	[1]
Electric sales:
Regulated	7,114		7,123		6,477
Nonregulated	3,334		3,829		3,802
Gas sales:
Regulated	287		308		494
Nonregulated	1,635		2,010		2,315
Gas transportation and storage	1,506		1,493		1,268
Other	503		434		442
Total operating revenue	$ 14,379		$ 15,197		$ 14,798

[1] Includes income tax expense of $21 million and $16 million in 2010 and 2009, respectively.