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Stock-Based Compensation Plans - Summary of Transactions of the Company's Stock Option Plans (Detail) - Stock Options Plan [Member]
6 Months Ended
Jun. 30, 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 (79,916)
Forfeited, Number of Options | shares (9,122)
Outstanding, Number of Options, Ending balance | shares 536,073
Outstanding, Weighted Average Exercise Price, Beginning balance $ 32.46
Exercised, Weighted Average Exercise Price 14.67
Forfeited, Weighted Average Exercise Price 32.39
Outstanding, Weighted Average Exercise Price, Ending balance 32.13
Outstanding, Weighted Average Grant-Date Fair Value 36.06
Exercised 27.42
Forfeited, Weighted Average Grant-Date Fair Value 40.47
Outstanding, Weighted Average Grant-Date Fair Value $ 41.43
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 12,632
Granted, Weighted Average Exercise Price $ 81.07
Granted, Weighted Average Grant-Date Fair Value $ 22.69