Reconciliation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Numerator:
Net income used for calculating basic and diluted earnings per share	$ 32,223		$ 20,113		$ 61,414		$ 39,516
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	96,886		95,657		96,664		95,810
Common stock equivalents associated with stock-based compensation plans	2,454	[1],[2]	3,198	[1],[2]	2,978	[1],[2]	3,879	[1],[2]
Shares used in the calculation of diluted earnings per share	99,340		98,855		99,642		99,689
Basic earnings per share	$ 0.33		$ 0.21		$ 0.64		$ 0.41
Diluted earnings per share	$ 0.32		$ 0.20		$ 0.62		$ 0.40

[1] For the six months ended June 30, 2011 and 2010, 0.3 million and 0.4 million respectively, of common stock equivalents were not included in the computation of diluted earnings per share because the effect would have been anti-dilutive.

[2] For the three months ended June 30, 2011 and 2010, 0.8 million and 1.6 million respectively, of common stock equivalents were not included in the computation of diluted earnings per share because the effect would have been anti-dilutive.