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Stock-Based Compensation Plans - Summary of Transactions of the Company's Stock Option Plans (Detail) - Stock Options Plan [Member]
3 Months Ended
Mar. 31, 2019
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Outstanding, Number of Options, Beginning balance | shares 545,249
Exercised, Number of Options | shares (70,632)
Forfeited, Number of Options | shares (1,584)
Outstanding, Number of Options, Ending balance | shares 552,802
Outstanding, Weighted Average Exercise Price, Beginning balance $ 32.46
Exercised, Weighted Average Exercise Price 13.78
Forfeited, Weighted Average Exercise Price 62.39
Outstanding, Weighted Average Exercise Price, Ending balance 31.92
Outstanding, Weighted Average Grant-Date Fair Value 36.06
Exercised 27.78
Forfeited, Weighted Average Grant-Date Fair Value 26.57
Outstanding, Weighted Average Grant-Date Fair Value $ 41.16
Discount [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted, Number of Options | shares 67,230
Granted, Weighted Average Exercise Price $ 0.00
Granted, Weighted Average Grant-Date Fair Value $ 71.54
Market Value [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted, Number of Options | shares 12,539
Granted, Weighted Average Exercise Price $ 81.07
Granted, Weighted Average Grant-Date Fair Value $ 22.69