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, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Numerator:
Net income used for calculating basic and diluted earnings per share	$ 38,194		$ 31,375		$ 121,383		$ 107,080
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	92,689		93,522		93,286		93,429
Common stock equivalents associated with stock-based compensation plans	1,666	[1]	2,089	[1]	1,814	[1]	2,362	[1]
Shares used in the calculation of diluted earnings per share	94,355		95,611		95,100		95,791
Basic earnings per share (in Dollars per share)	$ 0.41		$ 0.34		$ 1.30		$ 1.15
Diluted earnings per share (in Dollars per share)	$ 0.40		$ 0.33		$ 1.28		$ 1.12

[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 for both the three months ended September 30, 2013 and 2012 and 0.3 million and 0.7 million for the nine months ended September 30, 2013 and 2012, respectively.