Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Summary Of Carrying And Fair Values Of Long-Term Debt

	September 30, 2018				December 31, 2017
	Carrying Value		Fair Value		Carrying Value		Fair Value
3.60% 2022 Senior Notes	$	249	$	246	$	249	$	255
3.60% 2026 Senior Notes	741		704		740		757
Loan related to tax-exempt waste disposal revenue bonds due 2027	11		11		11		11
6 ½% 2029 GO Zone Senior Notes	99		108		99		111
6 ½% 2035 GO Zone Senior Notes	88		96		88		99
6 ½% 2035 IKE Zone Senior Notes	65		70		65		74
5.0% 2046 Senior Notes	675		687		675		787
4.375% 2047 Senior Notes	491		446		491		518
3.50% 2032 GO Zone Refunding Senior Notes	248		241		248		256
4.625% Westlake 2021 Senior Notes	—		—		645		639
4.625% Subsidiary 2021 Senior Notes	—		—		65		65
4.875% Westlake 2023 Senior Notes	—		—		445		449
4.875% Subsidiary 2023 Senior Notes	—		—		16		16