Repurchases Of Common Stock (Schedule Of Common Stock Repurchases) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Repurchases Of Common Stock [Abstract]
Shares repurchased in the open market	465	390
Shares acquired through employee surrender for statutory tax withholding	48	52
Total shares repurchased	513	442
Cost of shares repurchased in the open market	$ 86,188	$ 50,744
Cost of shares for employee surrenders	8,555	7,303
Total cost of shares	$ 94,743	$ 58,047
Average cost per share - open market repurchase	$ 185.23	$ 130.12
Average cost per share - employee surrenders	178.83	141.09
Average cost per share - total	$ 184.63	$ 131.41