Calculations Of Basic And Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Numerator:
Net income used for calculating basic and diluted earnings per share	$ 41,484		$ 32,223		$ 75,705		$ 61,414
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	93,350		96,886		93,383		96,664
Common stock equivalents associated with stock-based compensation plans	2,073	[1]	2,454	[1]	2,443	[1]	2,978	[1]
Shares used in the calculation of diluted earnings per share	95,423		99,340		95,826		99,642
Basic earnings per share	$ 0.44		$ 0.33		$ 0.81		$ 0.64
Diluted earnings per share	$ 0.43		$ 0.32		$ 0.79		$ 0.62

[1] Certain common stock equivalents were not included in the computation of diluted earnings per share because the effect would have been anti-dilutive. These amounted to 0.7 million and 0.8 million for the three months ended June 30, 2012 and 2011, respectively, and 0.7 million and 0.3 million for the six months ended June 30, 2012 and 2011, respectively.