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Stock-Based Compensation (Tables)
 12 Months Ended
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 PricesOptions 
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:
OptionsWeighted
Average
Exercise
Price		Weighted
Average
Remaining
Term
(Years)		Aggregate
Intrinsic
Value
Outstanding at December 31, 20191,385,948 $60.29 
Granted462,007 65.81 
Exercised(247,414)23.78 
Cancelled(21,671)77.46 
Outstanding at December 31, 20201,578,870 $67.39 6.8$27 
Exercisable at December 31, 2020877,908 $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,
202020192018
Weighted average fair value$15.55 $21.02 $28.94 
Risk-free interest rate1.4 %2.5 %2.7 %
Expected life in years555
Expected volatility29.4 %28.9 %27.6 %
Expected dividend yield1.6 %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, 2019463,283 $78.69 
Granted368,868 65.09 
Vested(193,550)64.10 
Forfeited(18,945)76.42 
Non-vested at December 31, 2020619,656 $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, 201977,217 $114.38 
Granted109,552 74.61 
Vested— — 
Forfeited(2,979)88.23 
Non-vested at December 31, 2020183,790 $91.10 
Schedule Of Share Based Payment Award Performance Share Units Valuation Assumptions [Table Text Block]
Performance Stock Units
Year Ended December 31,
20202019
Risk-free interest rate1.4 %2.5 %
Expected life in years2.882.88
Expected volatility of Westlake Chemical Corporation common stock32.0 %30.3 %
Expected volatility of peer companies
15.7% - 47.4%
14.5% - 47.8%
Average correlation coefficient of peer companies0.490.49
Grant date fair value$74.61 $114.38