Schedule I Condensed Financial Information Parent Company Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements [Line Items]
Total Cash Flows from Operating Activities	$ 1,038	$ 773	$ 924
Cash Flows from Investing Activities:
Capital expenditures	(1,127)	(1,043)	(944)
Asset dispositions	16	76	70
Capital contributions and loans	0	0	0
Capital redemptions and loans	0	0	0
Other transactions	17	(26)	15
Total Cash Flows from Investing Activities	(1,123)	(902)	(859)
Cash Flows from Financing Activities:
Short term debt and overdrafts incurred	77	179	85
Short term debt and overdrafts paid	(156)	(138)	(68)
Long term debt incurred	3,531	3,171	1,750
Long term debt paid	(3,717)	(2,650)	(1,555)
Proceeds from issuance of preferred stock	0	484	0
Preferred stock dividends paid	(29)	(15)	0
Common stock issued	3	8	1
Capital contributions and loans	0	0	0
Capital redemptions and loans	0	0	0
Transactions with minority interests in subsidiaries	(71)	(24)	(13)
Debt related costs and other transactions	(64)	(21)	(21)
Total Cash Flows from Financing Activities	(426)	994	179
Net Change in Cash and Cash Equivalents	(491)	767	83
Cash and Cash Equivalents at Beginning of the Year	2,772	2,005	1,922
Cash and Cash Equivalents at End of the Year	2,281	2,772	2,005
Parent [Member]
Condensed Financial Statements [Line Items]
Total Cash Flows from Operating Activities	335	260	278
Cash Flows from Investing Activities:
Capital expenditures	(231)	(210)	(334)
Asset dispositions	5	69	1
Capital contributions and loans	(191)	(14)	0
Capital redemptions and loans	81	0	16
Other transactions	5	(2)	26
Total Cash Flows from Investing Activities	(331)	(157)	(291)
Cash Flows from Financing Activities:
Short term debt and overdrafts incurred	0	0	3
Long term debt incurred	800	400	994
Long term debt paid	(762)	(750)	(974)
Proceeds from issuance of preferred stock	0	484	0
Preferred stock dividends paid	(29)	(15)	0
Common stock issued	3	8	1
Capital contributions and loans	150	(101)	0
Capital redemptions and loans	(200)	0	0
Transactions with minority interests in subsidiaries	(17)	(3)	0
Debt related costs and other transactions	(63)	(2)	(21)
Total Cash Flows from Financing Activities	(118)	21	3
Net Change in Cash and Cash Equivalents	(114)	124	(10)
Cash and Cash Equivalents at Beginning of the Year	916	792	802
Cash and Cash Equivalents at End of the Year	$ 802	$ 916	$ 792