Net Income Per Common Share - Average Exercise Prices of Options Excluded from Computation of Diluted Net Income Per Common Share (Detail) - $ / shares |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Abstract] | ||||
Shares | 75,543 | 283,130 | 39,120 | 366,628 |
Average Exercise Price | $ 46.46 | $ 30.32 | $ 46.10 | $ 29.87 |