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Stock-Based Compensation Plans - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2020 | Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock option compensation | $ 1.2 | $ 1.6
Stock Options Plan [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Number exercisable and fully vested | 49,444 |
Fully vested stock options with performance conditions attached | 12,519 |
Stock option compensation | $ 1.2 | 1.6
Total intrinsic value exercised | 4.2 | 2.1
Total compensation cost related to non-vested stock options not yet recognized | $ 11.9 |
Expected compensation cost recognized over the weighted-average period | 2 years 1 month 9 days |
Stock Equivalent Units [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Fully vested stock options with performance conditions attached | 56,664 |
Total intrinsic value exercised | $ 5.6 | 6.2
Expected compensation cost recognized over the weighted-average period | 2 years 4 months 20 days |
Number of exercisable SEUs | 63,196 |
Compensation cost | $ 6.0 | $ 7.5

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