Earnings per Share (Detail) - Calculations Of Basic And Diluted Earnings Per Share (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
Numerator:
Net income used for calculating basic and diluted earnings per share	$ 46,514		$ 41,484		$ 83,189		$ 75,705
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	93,574		93,350		93,584		93,383
Common stock equivalents associated with stock-based compensation plans	1,614	[1]	2,073	[1]	1,842	[1]	2,443	[1]
Shares used in the calculation of diluted earnings per share	95,188		95,423		95,426		95,826
Basic earnings per share (in Dollars per share)	$ 0.50		$ 0.44		$ 0.89		$ 0.81
Diluted earnings per share (in Dollars per share)	$ 0.49		$ 0.43		$ 0.87		$ 0.79

[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 shares totaled 0.4 million and 0.7 million for the three months ended June 30, 2013 and 2012, respectively, and 0.3 million and 0.7 million for the six months ended June 30, 2013 and 2012, respectively.