Debt (Schedule Of Short-term Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt [Abstract]
Balance at year-end
Average during the year	129,031	20,346	23,281
Maximum month-end balance	$ 300,000	$ 100,000	$ 50,000
Weighted average rate during the year (in hundredths)	2.43%	2.22%	1.39%
Rate at December 31 (in hundredths)	1.50%	2.35%	1.34%