Details of Basic and Diluted EPS (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Line Items]
Net income	$ 55,945	$ 50,262	$ 106,968	$ 95,801
Weighted average shares outstanding - basic	92,860	92,626	92,884	92,722
Dilutive effect of stock plans	2,180	2,302	2,219	2,337
Weighted average shares outstanding - diluted	95,040	94,928	95,103	95,059
Basic earnings per share	$ 0.60	$ 0.54	$ 1.15	$ 1.03
Diluted earnings per share	$ 0.59	$ 0.53	$ 1.12	$ 1.01
Anti-dilutive options	1,170	1,128	1,144	1,329