Supplemental Cash Flows Information (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash payments (receipts) for interest and taxes:
Interest - net of amounts capitalized	$ 550	$ 529
Tax refunds - net	(71)	(330)
Details of debt exchange:
Pollution-control bonds redeemed	0	(86)
Pollution-control bonds issued	0	86
Dividends declared but not paid:
Common stock	106	104
Preferred and preference stock	6	12
Accrued capital expenditures	$ 431	$ 393