Details of Basic and Diluted EPS (Detail) - 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
Earnings Per Share [Abstract]
Net income	$ 69,628	$ 62,335	$ 126,096	$ 118,467
Weighted average shares outstanding - basic	87,638	89,866	87,876	89,962
Dilutive effect of stock plans	1,667	1,860	1,818	1,971
Weighted average shares outstanding - diluted	89,305	91,726	89,694	91,933
Basic earnings per share	$ 0.79	$ 0.69	$ 1.43	$ 1.32
Diluted earnings per share	$ 0.78	$ 0.68	$ 1.41	$ 1.29
Anti-dilutive shares	169	223	228	230