Equity Incentive Plans (Summary Of Share Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	May 28, 2021	May 12, 2016
Maximum term of options granted, years	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Shares, Outstanding at Beginning of Period	116,690	118,030	234,875
Number of Shares, Exercised	(5,051)	(1,410)	(118,786)
Number of Shares, Granted	1,838	2,890	1,941
Number of Shares, Forfeited	(4,806)	(2,820)
Number of Shares, Outstanding at End of Period	108,671	116,690	118,030
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Average Exercise Price, Outstanding at Beginning of Period	$ 56.36	$ 55.63	$ 51.98
Average Exercise Price, Exercised	47.27	44.98	48.71
Average Exercise Price, Granted	44.44	69.19	73.84
Average Exercise Price, Forfeited	51.42	44.98
Average Exercise Price, Outstanding at End of Period	56.79	56.36	55.63
Weighted average fair value of options granted	$ 20.34	$ 3.73	$ 4.64
Intrinsic value of stock options exercised	$ 14	$ 22	$ 2,800
Share-based Compensation Arrangement by Share-based Payment Award, Repurchase of Treasury Shares	4,812
Share-based Compensation Arrangement by Share-based Payment Award, Repurchase of Treasury Value	$ 241
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Option Price Per Share [Roll Forward]
Option Price Per Share, Outstanding at Beginning of Period	$ 44.62	$ 44.62	$ 19.02
Option Price Per Share, Exercised	45.20	44.98	19.02
Option Price Per Share, Granted	44.44	69.19	73.84
Option Price Per Share, Forfeited	45.20	44.98
Option Price Per Share, Outstanding at End of Period	44.44	44.62	44.62
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Option Price Per Share [Roll Forward]
Option Price Per Share, Outstanding at Beginning of Period	76.63	76.63	76.63
Option Price Per Share, Exercised	47.77	44.98	61.79
Option Price Per Share, Granted	44.44	69.19	73.84
Option Price Per Share, Forfeited	61.79	44.98
Option Price Per Share, Outstanding at End of Period	$ 76.63	$ 76.63	$ 76.63
2016 Equity Incentive Plan [Member]
Common shares, options to purchase common shares and restricted share units, expected to granted				3,950,000	1,950,000
Number of shares available for grant	2,364,714