Schedule Of Valuation And Qualifying Accounts (Details) - Allowance for doubtful accounts [Member] - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 1,733,000	$ 105,000	$ 2,838,000
Charges to Operatons	10,323,000	1,718,000	1,697,000
Other additions	0	0	0
Deductions	1,971,000	90,000	4,430,000
Balance at end of period	$ 10,085,000	$ 1,733,000	$ 105,000