Other Liabilities And Provisions (Schedule Of Other Liabilities And Provisions) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Liabilities And Provisions [Line Items]
The Bow Office Building	$ 1,344	$ 1,266
Obligation under Capital Lease	295	304
Unrecognized Tax Benefits	306	286	$ 317
Pensions and Other Post-Employment Benefits	116	124
Long-Term Incentives	175	120
Other Derivative Contracts, Liabilities	19	19
Other	21	26
Other Liabilities and Provisions	2,167	2,047
Other Liabilities and Provisions [Member]
Other Liabilities And Provisions [Line Items]
Unrecognized Tax Benefits	202	193
Other Derivative Contracts, Liabilities	$ 14	$ 14