Calculations Of Basic And Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Numerator:
Net income used for calculating basic and diluted earnings per share	$ 34,221		$ 29,191
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	93,416		96,442
Common stock equivalents associated with stock-based compensation plans	2,783	[1]	3,009	[1]
Shares used in the calculation of diluted earnings per share	96,199		99,451
Basic earnings per share	$ 0.37		$ 0.30
Diluted earnings per share	$ 0.36		$ 0.29

[1] For the three months ended March 31, 2012 and 2011, 0.6 million and 1.2 million of common stock equivalents, respectively, were not included in the computation of diluted earnings per share because the effect would have been anti-dilutive.