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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 Restricted Stock and Restricted Stock Unit Activity | A summary of activity during 2020 related to NewMarket’s restricted stock and restricted stock units (stock awards) is presented below in whole shares:
|  | Number of Shares |  | Weighted Average Grant-Date Fair Value
Unvested stock awards at January 1, 2020 |  | 21,111 |  |  | $ | 427.14 |
Granted in 2020 |  | 6,779 |  |  | 414.33 |
Vested in 2020 |  | 4,708 |  |  | 428.54 |
Forfeited in 2020 |  | 2,268 |  |  | 428.07 |
Unvested stock awards at December 31, 2020 |  | 20,914 |  |  | 422.57 |

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- Definition Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
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- References No definition available. + Details
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