Additional Financial Information (Supplemental Statements of Cash Flows Information) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Additional Financial Information [Abstract]
Interest payments, net of amounts capitalized	$ 621	$ 639
Income tax payments	33	23
Increase (decrease) in accounts payable and accrued liabilities for purchases of property and equipment	(173)	56
Issuance of short-term debt for financing of property and equipment purchases	500	255
Assets acquired under capital lease obligations	$ 190	$ 63