Schedule I Condensed Financial Information Parent Company Balance Sheets Parenthetical (Details) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements [Line Items]
Allowance for Doubtful Accounts Receivable, Current	$ 89	$ 99
Accumulated depreciation	(9,029)	(9,158)
Preferred Stock, Shares Authorized	50,000,000	50,000,000
Preferred Stock, Shares Outstanding	0	10,000,000
Common Stock, Shares Authorized	450,000,000	450,000,000
Common Stock, Shares, Outstanding	269,000,000	248,000,000
Parent Company
Condensed Financial Statements [Line Items]
Allowance for Doubtful Accounts Receivable, Current	20	21
Accumulated depreciation	$ (4,084)	$ (4,032)
Preferred Stock, Shares Authorized		50,000,000
Preferred Stock, Shares Outstanding		10,000,000
Common Stock, Shares Authorized	450,000,000	450,000,000
Common Stock, Shares, Outstanding	269,000,000	248,000,000