Earnings and Dividends per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) - $ / shares |
3 Months Ended | |
|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
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| Earnings and Dividends Per Share [Abstract] | ||
| Weighted average common shares—basic | 128,528,480 | 129,483,968 |
| Weighted Average Number Diluted Shares Outstanding Adjustment | 385,441 | |
| Incremental Shares From Assumed exercise of options | 706,924 | |
| Weighted average common shares-diluted | 128,913,921 | 130,190,892 |
| Earnings per share attributable to Westlake Chemical Corporation: Basic | $ 0.56 | $ 2.21 |
| Earnings per share attributable to Westlake Chemical Corporation: Diluted | $ 0.55 | $ 2.20 |
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- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Earnings and Dividends Per Share [Abstract] No definition available.
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