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Stock Option Plan - Stock Options Issued (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2023 $ / shares | Dec. 31, 2022 $ / shares | Dec. 31, 2021 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | $ 0 | $ 44.44 | $ 45.07
Directors | May, 13 2022 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | 33.79 |  |
Fair value per option (in usd per share) | $ 6.53 |  |
Volatility | 0.319 |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.94% |  |
Risk-free rate | 3.45% |  |
Directors | May 7, 2021 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | $ 47.90 |  |
Fair value per option (in usd per share) | $ 8.34 |  |
Volatility | 0.300 |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.90% |  |
Risk-free rate | 2.89% |  |
Directors | April 24, 2020 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | $ 43.89 |  |
Fair value per option (in usd per share) | $ 6.32 |  |
Volatility | 0.297 |  |
Expected life (years) | 5 years |  |
Assumed yield | 4.96% |  |
Risk-free rate | 0.77% |  |
Officers | May, 13 2022 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | $ 33.79 |  |
Fair value per option (in usd per share) | $ 6.06 |  |
Volatility | 0.288 |  |
Expected life (years) | 7 years |  |
Assumed yield | 4.96% |  |
Risk-free rate | 3.45% |  |
Officers | May 7, 2021 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | $ 47.90 |  |
Fair value per option (in usd per share) | $ 7.66 |  |
Volatility | 0.271 |  |
Expected life (years) | 7 years |  |
Assumed yield | 4.93% |  |
Risk-free rate | 2.95% |  |
Officers | April 24, 2020 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercise price (in usd per share) | $ 43.89 |  |
Fair value per option (in usd per share) | $ 5.96 |  |
Volatility | 0.275 |  |
Expected life (years) | 7 years |  |
Assumed yield | 4.97% |  |
Risk-free rate | 1.24% |  |

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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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- Definition Line items represent financial concepts included in a table. 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