Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 51,662	$ 48,467
Average basic shares outstanding	57,889,000	58,330,000
Effect of dilutive stock options	991,000	1,222,000
Average diluted shares outstanding	58,880,000	59,552,000
Earnings per basic share	$ 0.89	$ 0.83
Earnings per diluted share	$ 0.88	$ 0.81
Average options excluded from computation of diluted earnings per share	1,600,000	500,000