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	$ 348	$ 321
Tax refunds - net	(8)	(44)
Noncash investing and financing activities:
Purchase of equipment with notes payable	0	56
Details of debt exchange:
Pollution-control bonds redeemed	0	(56)
Pollution-control bonds issued	0	56
Dividends declared but not paid:
Common stock	106	104
Preferred and preference stock	34	15
Accrued capital expenditures	$ 433	$ 388