Earnings Per Common Share And Share Awards Summary Of Share-Based Award Transactions (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				9 Months Ended	12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, SARS, Outstanding [Roll Forward]
Number Of Shares, SARs granted	4	7	4
SARs
Share-based Compensation Arrangement by Share-based Payment Award, SARS, Outstanding [Roll Forward]
Number Of Shares, Outstanding Beginning Balance		30		28	30	28
Number Of Shares, SARs granted				0	11	4
Number Of Shares, SARS exercised					(8)	(2)
Number Of Shares, Outstanding Ending Balance					33	30	28
Number Of Shares, Exercisable as of September 30, 2020					26
Number Of Shares, Unvested as of September 30, 2020					7
Share-based Compensation Arrangement by Share-based Payment Award, SARs, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Outstanding Beginning Balance		$ 124.13		$ 110.27	$ 124.13	$ 110.27
Weighted Average Exercise Price, SARs granted					135.05	162.81
Weighted Average Exercise Price, SARS exercised					75.75	50.50
Weighted Average Exercise Price, Outstanding Ending Balance					138.55	$ 124.13	$ 110.27
Weighted Average Exercise Price, Exercisable as of September 30, 2020					140.02
Weighted Average Exercise Price, Unvested as of September 30, 2020					$ 133.21
Average Remaining Contractual Term, Outstanding Beginning Balance					4 years 4 months 28 days	3 years 6 months 10 days	3 years 7 months 20 days
Average Remaining Contractual Term, Outstanding Ending Balance					4 years 4 months 28 days	3 years 6 months 10 days	3 years 7 months 20 days
Average Remaining Contractual Term, Exercisable as of September 30, 2020					3 years 9 months 29 days
Average Remaining Contractual Term, Unvested as of September 30, 2020					6 years 6 months 7 days
Aggregate Intrinsic Value, Outstanding Beginning Balance		$ 1,352		$ 2,019	$ 1,352	$ 2,019
Aggregate Intrinsic Value, Outstanding Ending Balance					496	$ 1,352	$ 2,019
Aggregate Intrinsic Value, Exercisable as of September 30, 2020					480
Aggregate Intrinsic Value, Unvested as of September 30, 2020					$ 16