Shareholders' Equity (Summary Of Activities In Common Stock) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shareholders' Equity [Abstract]
Purchases of common stock, Shares	(3,004)	(3,559)	(1,235)
Purchases of common stock, Amount	$ (71,802)	$ (65,793)	$ (17,000)
Stock option exercises, Shares	582	615	425
Stock option exercises, Amount	3,553	3,181	2,295
Employee stock plan purchases, Shares	100	118	115
Employee stock plan purchases, Amount	$ 2,045	$ 1,825	$ 1,428