Computation of Earnings Per Share (Detail) - Calculations Of Basic And Diluted Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 193,582	$ 175,635	$ 183,766
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	82,571	83,852	89,337
Common share equivalents associated with stock-based compensation plans	1,249	1,204	1,382
Shares used in the calculation of diluted earnings per share	83,820	85,056	90,719
Earnings per share:
Basic (in Dollars per share)	$ 2.34	$ 2.09	$ 2.06
Diluted (in Dollars per share)	$ 2.31	$ 2.06	$ 2.03