Summary Of Significant Accounting Policies (Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Net income	$ 252,521	$ 254,690	$ 245,327
Weighted average shares outstanding - basic	89,561	92,067	92,691
Dilutive effect of stock plans	1,941	2,127	2,448
Weighted average shares outstanding - diluted	91,502	94,194	95,139
Basic earnings per share (in USD per share)	$ 2.82	$ 2.77	$ 2.65
Diluted earnings per share (in USD per share)	$ 2.76	$ 2.70	$ 2.58
Anti-dilutive options	206	718	885