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Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2020
Share-based Payment Arrangement, Noncash Expense [Abstract] |
Schedule Of Range Of Exercise Prices For Outstanding Options | For options outstanding at December 31, 2020, the options had the following range of exercise prices:
Range of Prices |  | Options Outstanding |  | Weighted Average Remaining Contractual Life (Years)
$30.05 - $45.70 |  | 309,149 |  |  | 3.6
$61.87 - $63.98 |  | 280,044 |  |  | 5.6
$65.81 - $65.81 |  | 453,311 |  |  | 9.1
$68.09 - $79.83 |  | 369,495 |  |  | 7.2
$107.75 - $107.75 |  | 166,871 |  |  | 7.1
Schedule Of Option Activity And Changes | Option activity and changes during the year ended December 31, 2020 were as follows:
|  | Options |  | Weighted Average Exercise Price |  | Weighted Average Remaining Term (Years) |  | Aggregate Intrinsic Value
Outstanding at December 31, 2019 |  | 1,385,948 |  |  | $ | 60.29 |  |  |  |  |
Granted |  | 462,007 |  |  | 65.81 |  |  |  |  |
Exercised |  | (247,414) |  |  | 23.78 |  |  |  |  |
Cancelled |  | (21,671) |  |  | 77.46 |  |  |  |  |
Outstanding at December 31, 2020 |  | 1,578,870 |  |  | $ | 67.39 |  |  | 6.8 |  | $ | 27 |
Exercisable at December 31, 2020 |  | 877,908 |  |  | $ | 62.91 |  |  | 5.2 |  | $ | 19 |
Schedule Of Weighted Average Value And Assumptions For Fair Value Of Options | The Company used the Black-Scholes option pricing model to value its options. The table below presents the weighted average value and assumptions used in determining each option's fair value. Volatility was calculated using historical trends of the Company's common stock price.
|  | Stock Option Grants
|  | Year Ended December 31,
|  | 2020 |  | 2019 |  | 2018
Weighted average fair value |  | $ | 15.55 |  |  | $ | 21.02 |  |  | $ | 28.94 |
Risk-free interest rate |  | 1.4 | % |  | 2.5 | % |  | 2.7 | %
Expected life in years |  | 5 |  | 5 |  | 5
Expected volatility |  | 29.4 | % |  | 28.9 | % |  | 27.6 | %
Expected dividend yield |  | 1.6 | % |  | 1.2 | % |  | 0.7 | %
Schedule Of Non-Vested Restricted Stock Award Activity And Changes | Non-vested restricted stock units as of December 31, 2020 and changes during the year ended December 31, 2020 were as follows:
|  | Number of Units |  | Weighted Average Grant Date Fair Value
Non-vested at December 31, 2019 |  | 463,283 |  |  | $ | 78.69 |
Granted |  | 368,868 |  |  | 65.09 |
Vested |  | (193,550) |  |  | 64.10 |
Forfeited |  | (18,945) |  |  | 76.42 |
Non-vested at December 31, 2020 |  | 619,656 |  |  | $ | 75.22 |
Share-based Payment Arrangement, Performance Shares, Activity [Table Text Block] |
|  | Number of Units |  | Weighted Average Grant Date Fair Value
Non-vested at December 31, 2019 |  | 77,217 |  |  | $ | 114.38 |
Granted |  | 109,552 |  |  | 74.61 |
Vested |  | — |  |  | — |
Forfeited |  | (2,979) |  |  | 88.23 |
Non-vested at December 31, 2020 |  | 183,790 |  |  | $ | 91.10 |
Schedule Of Share Based Payment Award Performance Share Units Valuation Assumptions [Table Text Block] |
|  | Performance Stock Units
|  | Year Ended December 31,
|  | 2020 |  | 2019
Risk-free interest rate |  | 1.4 | % |  | 2.5 | %
Expected life in years |  | 2.88 |  | 2.88
Expected volatility of Westlake Chemical Corporation common stock |  | 32.0 | % |  | 30.3 | %
Expected volatility of peer companies |  | 15.7% - 47.4% |  | 14.5% - 47.8%
Average correlation coefficient of peer companies |  | 0.49 |  | 0.49
Grant date fair value |  | $ | 74.61 |  |  | $ | 114.38 |

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- Definition Tabular disclosure of option exercise prices, by grouped ranges, including the upper and lower limits of the price range, the number of shares under option, weighted average exercise price and remaining contractual option terms. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of number, weighted-average exercise price or conversion ratio, aggregate intrinsic value, and weighted-average remaining contractual term for outstanding and exercisable options that are fully vested and expected to vest. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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