Equity Incentive Plans (Summary Of Exercisable Options) (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares
Options outstanding (in shares) | shares	109,875
Weighted avg. life remaining (in years)	3 years 9 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 55.67
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value | $	$ 0
Forty Four Point Sixty Two To Forty Nine Point Nine Nine [Member]
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit	$ 44.62
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 49.99
Options outstanding (in shares) | shares	27,215
Weighted avg. life remaining (in years)	1 year 9 months 18 days
Fifty To Fifty Nine Point Nine Nine Member
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit	$ 50.00
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 59.99
Options outstanding (in shares) | shares	29,793
Weighted avg. life remaining (in years)	3 years 9 months 18 days
Sixty To Sixty Five Point Five Zero Member
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit	$ 60.00
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 69.99
Options outstanding (in shares) | shares	50,719
Weighted avg. life remaining (in years)	4 years 7 months 6 days
Seventy To Seventy Six Point Six Three [Member]
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit	$ 70.00
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 76.63
Options outstanding (in shares) | shares	2,148
Weighted avg. life remaining (in years)	7 years 1 month 6 days