Goodwill, Intangibles and Other Assets (Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance at beginning of year	$ 947	$ 62
Goodwill acquired during the year		888
Effects of changes in foreign exchange rates	10	(3)
Goodwill, Purchase Accounting Adjustments	55
Balance at end of year	1,012	947
Olefins [Member]
Goodwill [Roll Forward]
Balance at beginning of year	30	30
Goodwill acquired during the year		0
Effects of changes in foreign exchange rates	0	0
Goodwill, Purchase Accounting Adjustments	0
Balance at end of year	30	30
Vinyls [Member]
Goodwill [Roll Forward]
Balance at beginning of year	917	32
Goodwill acquired during the year		888
Effects of changes in foreign exchange rates	10	(3)
Goodwill, Purchase Accounting Adjustments	55
Balance at end of year	$ 982	$ 917