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, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 175,635	$ 183,766	$ 182,801
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	83,852	89,337	93,015
Common share equivalents associated with stock-based compensation plans	1,204	1,382	1,815
Shares used in the calculation of diluted earnings per share	85,056	90,719	94,830
Earnings per share:
Basic (in Dollars per share)	$ 2.09	$ 2.06	$ 1.97
Diluted (in Dollars per share)	$ 2.06	$ 2.03	$ 1.93