Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Receivables, allowances for uncollectible accounts (in dollars)	$ 75	$ 75
Utility property, plant and equipment, accumulated depreciation (in dollars)	7,378	6,894
Competitive power generation and other property, plant and equipment, accumulated depreciation (in dollars)	$ 1,616	$ 1,408
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	800,000,000	800,000,000
Common stock, shares issued	325,811,206	325,811,206
Common stock, shares outstanding	325,811,206	325,811,206