Details of Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 69,557	$ 66,033	$ 195,653	$ 184,500
Weighted average shares outstanding - basic	86,959	89,694	87,570	89,873
Dilutive effect of stock plans	1,717	1,899	1,785	1,947
Weighted average shares outstanding - diluted	88,676	91,593	89,355	91,820
Basic earnings per share	$ 0.80	$ 0.74	$ 2.23	$ 2.05
Diluted earnings per share	$ 0.78	$ 0.72	$ 2.19	$ 2.01
Anti-dilutive shares	269	204	242	221