Segment And Geographic Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017 plant Segment customer	Dec. 31, 2016 customer	Dec. 31, 2015 customer
Segment Reporting Information [Line Items]
Number of segments | Segment	2
Number of Building Product Facilities | plant	24
Olefins [Member]
Segment Reporting Information [Line Items]
Number of major customers	0	0	0
Vinyls [Member]
Segment Reporting Information [Line Items]
Number of major customers	0	0	0