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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, 2018
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Outstanding, Number of Options, Beginning balance | shares 357,666
Exercised, Number of Options | shares (69,569)
Forfeited, Number of Options | shares (11,874)
Outstanding, Number of Options, Ending balance | shares 366,300
Outstanding, Weighted Average Exercise Price, Beginning balance $ 13.74
Exercised, Weighted Average Exercise Price 13.83
Forfeited, Weighted Average Exercise Price 19.69
Outstanding, Weighted Average Exercise Price, Ending balance 13.66
Outstanding, Weighted Average Grant-Date Fair Value 35.69
Exercised 26.40
Forfeited, Weighted Average Grant-Date Fair Value 27.17
Outstanding, Weighted Average Grant-Date Fair Value $ 40.97
Discount [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted, Number of Options | shares 71,227
Granted, Weighted Average Exercise Price $ 0.00
Granted, Weighted Average Grant-Date Fair Value $ 57.53
Market Value [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted, Number of Options | shares 18,850
Granted, Weighted Average Exercise Price $ 68.20
Granted, Weighted Average Grant-Date Fair Value $ 16.23