Equity Incentive Plans (Summary Of Outstanding Options) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Exercise price range, lower limit	$ 61.79	$ 51.64	$ 46.86
Exercise price range, upper limit		$ 65.50	$ 65.50
Options outstanding	285,986	516,305	950,214	840,665
Weighted avg. life remaining	6 years 1 month
Weighted avg. exercise price	$ 51.93	$ 48.42	$ 42.48	$ 40.85
Aggregate intrinsic value	$ 5,673
$ 19.02 - 19.99
Exercise price range, lower limit	$ 19.02
Exercise price range, upper limit	$ 19.99
Options outstanding	11,097
Weighted avg. life remaining	2 years 5 months
20.00 - 29.99 [Member]
Exercise price range, lower limit	$ 20.00
Exercise price range, upper limit	$ 29.99
Options outstanding	0
30.00 - 39.99 [Member]
Exercise price range, lower limit	$ 30.00
Exercise price range, upper limit	$ 39.99
Options outstanding	1,428
Weighted avg. life remaining	3 years
40.00 - 49.99 [Member]
Exercise price range, lower limit	$ 40.00
Exercise price range, upper limit	$ 49.99
Options outstanding	96,122
Weighted avg. life remaining	4 years 8 months
50.00 - 59.99 [Member]
Exercise price range, lower limit	$ 50.00
Exercise price range, upper limit	$ 59.99
Options outstanding	84,934
Weighted avg. life remaining	6 years 7 months
60.00 - 61.79 [Member]
Exercise price range, lower limit	$ 60.00
Exercise price range, upper limit	$ 61.79
Options outstanding	92,405
Weighted avg. life remaining	7 years 7 months