Summary Of Significant Accounting Policies 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	Dec. 31, 2015
Accounting Policies [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 5,233	$ 5,132	$ 5,026	$ 4,530
Provision for Doubtful Accounts	3,917	5,317	6,053
Allowance for Doubtful Accounts Receivable, Write-offs	$ (3,816)	$ (5,211)	$ (5,557)