Earnings per Share (Detail) - Calculations Of Basic And Diluted Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 47,911	$ 51,155	$ 88,078	$ 79,506
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	82,559	83,203	82,505	84,871
Common stock equivalents associated with stock-based compensation plans (in shares)	917	1,068	993	1,193
Shares used in the calculation of diluted earnings per share	83,476	84,271	83,498	86,064
Basic earnings per share (in dollars per share)	$ 0.58	$ 0.61	$ 1.07	$ 0.94
Diluted earnings per share (in dollars per share)	$ 0.57	$ 0.61	$ 1.05	$ 0.92