Description of Operations and Summary of Significant Accounting Policies - Summary of Activity within Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Balance at beginning of period	$ 122	$ 289	$ 450
Charges, net of reversals	291	(93)	(3)
Write-offs		(74)	(158)
Balance at end of period	$ 413	$ 122	$ 289