Summary of Significant Accounting Policies (Allowance For Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, Net [Abstract]
Balance at beginning of year	$ 2,300	$ 2,156	$ 2,046
Additions:
Charged to costs and expense	2,855	3,141	2,427
Recovery of previous write-offs	1,215	1,122	1,395
Uncollectible receivables written off	4,300	4,119	3,712
Balance at end of year	$ 2,070	$ 2,300	$ 2,156