Summary of Significant Accounting Policies (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in the allowance for doubtful accounts
Balance, beginning of year	$ 1,190	$ 673	$ 579
Charged to provision for doubtful accounts, net of recoveries	512	839	157
Write-offs	(175)	(322)	(63)
Balance, end of year	$ 1,527	$ 1,190	$ 673