Property, Plant and Equipment, Net of Accumulated Depreciation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment, Net of Accumulated Depreciation [Abstract]
Interest Costs Capitalized	$ 36	$ 23	$ 35
Precious Metals	3,000	3,000
Depletion	$ 13	$ 20	$ 19