Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Cash Paid For Interest	$ 533	$ 458	$ 438
Cash Paid For Income Taxes	479	663	477
Non-cash Activities [Abstract]
Declared but unpaid dividends	61	60	61
Issuance of stock upon vesting of restricted stock units	125	127	131
Fair value of investments contributed to defined benefit plans		16
Cash and cash equivalents	1,335	786
Restricted Cash Included in Other Current Assets	24	18
Restricted Cash Included in Other Assets	2	7
Cash, Cash Equivalents and Restricted Cash	$ 1,361	$ 811	$ 466	$ 1,364
Restricted Cash and Cash Equivalents, Current, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsCurrent
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent