Supplemental Cash Flows Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash payments (receipts) for interest and taxes:
Interest - net of amounts capitalized	$ 713,000,000	$ 609,000,000	$ 661,000,000
Tax payments (refunds)- net	(332,000,000)	232,000,000	427,000,000
Details of assets acquired:
Fair value of assets acquired	1,000,000	1,000,000	14,000,000
Liabilities assumed	0	0	3,000,000
Net assets acquired	1,000,000	1,000,000	11,000,000
Noncash investing and financing activities:
Accrued capital expenditures	639,000,000	680,000,000	448,000,000
Details of debt exchange:
Pollution-control bonds redeemed	(86,000,000)	(378,000,000)	0
Pollution-control bonds issued	86,000,000	378,000,000	0
Details of capital lease obligations:
Capital lease purchased	0	0	(223,000,000)
Capital lease obligation issued	0	0	223,000,000
Consolidation of variable interest entities:
Assets other than cash	0	(94,000,000)	3,000,000
Liabilities and noncontrolling interests	0	99,000,000	(4,000,000)
Deconsolidation of variable interest entities:
Assets other than cash	0	380,000,000	0
Liabilities and noncontrolling interests	0	(476,000,000)	0
Dividends declared but not paid:
Common stock	106,000,000	104,000,000	103,000,000
Preferred and preference stock	$ 11,000,000	$ 13,000,000	$ 13,000,000