Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating Activities [Abstract]
Net income	$ 1,088	$ 957
Adjustments to reconcile net income to cash provided by operating activities [Abstract]
Depreciation	464	434
Deferred income taxes and unrecognized tax benefits	75	184
Other operating activities, net	(57)	4
Changes in current assets and liabilities [Abstract]
Accounts receivable, net	(128)	(181)
Materials and supplies	(52)	5
Other current assets	(93)	(14)
Accounts payable and other current liabilities	84	(82)
Income and other taxes payable	386	217
Cash provided by operating activities	1,767	1,524
Investing Activities [Abstract]
Capital investments	(893)	(782)
Proceeds from asset sales	27	17
Other investing activities, net	(39)	(35)
Cash used in investing activities	(905)	(800)
Financing Activities [Abstract]
Debt issued (Note 13)	995	944
Common share repurchases (Note 16)	(644)	(374)
Debt repaid	(402)	(83)
Dividends paid	(363)	(323)
Other financing activities, net	(23)	(34)
Cash (used in)/provided by financing activities	(437)	130
Net change in cash and cash equivalents	425	854
Cash and cash equivalents at beginning of year	1,432	1,063
Cash and cash equivalents at end of period	1,857	1,917
Non-cash investing and financing activities [Abstract]
Cash dividends declared but not yet paid	407	318
Capital investments accrued but not yet paid	109	107
Common shares repurchased but not yet paid	39	20
Cash paid for: [Abstract]
Income taxes, net of refunds	(146)	(39)
Interest, net of amounts capitalized	$ (178)	$ (179)