| Document and Entity Information | Aug. 05, 2021 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | WESTLAKE CHEMICAL CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0001262823 |
| Document Type | 8-K |
| Document Period End Date | Aug. 5, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-32260 |
| Entity Tax Identification Number | 76-0346924 |
| Entity Address, Address Line One | 2801 Post Oak Boulevard |
| Entity Address, Address Line Two | Suite 600 |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77056 |
| City Area Code | (713) |
| Local Phone Number | 960-9111 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, $0.01 par value |
| Trading Symbol | WLK |
| Security Exchange Name | NYSE |
| Senior Notes [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.625% Senior Notes due 2029 |
| Trading Symbol | WLK29 |
| Security Exchange Name | NYSE |
