Accounts Receivable (Allowance For Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable [Abstract]
Balance at January 1	$ 6,914	$ 7,071	$ 7,095
Amounts charged to expense	5,306	5,305	4,986
Accounts written off	(5,980)	(6,587)	(6,135)
Recoveries of accounts written off	1,113	1,125	1,125
Balance at December 31	$ 7,353	$ 6,914	$ 7,071