Reconciliation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 136,902		$ 96,285		$ 82,964
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	96,019		95,747		94,658
Common share equivalents associated with stock-based compensation plans	2,827		4,087		2,891
Shares used in the calculation of diluted earnings per share	98,846	[1]	99,834	[1]	97,549	[1]
Earnings per share:
Basic	$ 1.43		$ 1.01		$ 0.88
Diluted	$ 1.39		$ 0.96		$ 0.85

[1] During 2011, 2010 and 2009, the Company repurchased 5.9 million, 3.9 million, and 0.3 million shares of its Common Stock, respectively.