Summary of Significant Accounting Policies - Schedule of Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable
Balance at beginning of year	$ 387	$ 425	$ 477
Provision and reserve adjustments		285	2
Write-offs less recoveries	(27)	(323)	(54)
Balance at end of year	$ 360	$ 387	$ 425