Supplemental Cash Flows Information (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash payments (receipts) for interest and taxes:
Interest - net of amounts capitalized	$ 194	$ 179
Tax refunds - net	(2)	(95)
Details of debt exchange:
Pollution-control bonds redeemed	0	(56)
Pollution-control bonds issued	0	56
Dividends declared but not paid:
Preferred and preference stock	34	15
Accrued capital expenditures	$ 408	$ 341