Accounts Receivable (Allowance For Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable [Abstract]
Balance at January 1	$ 7,071	$ 7,095	$ 5,873
Amounts charged to expense	5,305	4,986	5,500
Accounts written off	(6,587)	(6,135)	(5,410)
Recoveries of accounts written off	1,125	1,125	1,132
Balance at December 31	$ 6,914	$ 7,071	$ 7,095