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				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Numerator:
Net income used for calculating basic and diluted earnings per share (in Dollars)	$ 31,375		$ 30,464		$ 107,080		$ 91,878
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	93,522		96,057		93,429		96,462
Common stock equivalents associated with stock-based compensation plans (1)	2,089	[1]	2,202	[1]	2,362	[1]	3,005	[1]
Shares used in the calculation of diluted earnings per share	95,611		98,259		95,791		99,467
Basic earnings per share (in Dollars per share)	$ 0.34		$ 0.32		$ 1.15		$ 0.95
Diluted earnings per share (in Dollars per share)	$ 0.33		$ 0.31		$ 1.12		$ 0.92

[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 0.4 million and 1.6 million for the three months ended September 30, 2012 and 2011, respectively, and 0.7 million and 0.3 million for the nine months ended September 30, 2012 and 2011, respectively.