Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Receivables, allowances for uncollectible accounts (in dollars)	$ 75	$ 85
Utility property, plant and equipment, accumulated depreciation (in dollars)	6,894	6,319
Competitive power generation and other property, plant and equipment, accumulated depreciation (in dollars)	$ 1,408	$ 1,865
Common stock, no par value (in dollars per share)
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