Earnings Per Share (Summary Of Earnings Per Share, Basic And Diluted) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share Basic And Diluted By Common Class [Line Items]
Net income	$ 54,401	$ 36,715	$ 96,480	$ 69,049
Weighted-average shares outstanding	82,430,000	78,929,000	82,054,000	78,673,000
Share-based payment awards classified as participating securities	863,000	1,222,000	876,000	1,371,000
Denominator for basic earnings per share	83,294,000	80,151,000	82,929,000	80,044,000
Dilutive securities	2,444,000	3,397,000	2,521,000	3,420,000
Denominator for diluted earnings per share	85,737,000	83,548,000	85,451,000	83,464,000
Basic earnings per share	$ 0.65	$ 0.46	$ 1.16	$ 0.86
Diluted earnings per share	$ 0.63	$ 0.44	$ 1.13	$ 0.83
Diluted earnings per share excludes antidilutive effect	200,000	200,000
Earnings Per Share, Basic [Member]
Earnings Per Share Basic And Diluted By Common Class [Line Items]
Net income	$ 54,401	$ 36,715	$ 96,480	$ 69,049