Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Statement of Financial Position [Abstract]
Receivables, allowances for uncollectible accounts (in dollars)	$ 75	$ 85
Utility property, plant and equipment, less accumulated depreciation of $6,894 and $6,319 at respective dates	6,894	6,319
Nonutility property, plant and equipment, less accumulated depreciation of $107 and $100 at respective dates	$ 107	$ 100
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	560,000,000	560,000,000
Common stock, shares issued	434,888,104	434,888,104
Common stock, shares outstanding	434,888,104	434,888,104