Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 669	$ 802
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	170,000,000	170,000,000
Common stock issued (in shares)	10,390,524	10,387,926
Common stock outstanding (in shares)	10,347,806	10,345,367
Treasury stock (in shares)	42,718	42,559
Convertible Preferred Stock
Convertible preferred stock par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock authorized (in shares)	5,000,000	5,000,000
Convertible preferred stock issued (in shares)	0	0
Convertible preferred stock outstanding (in shares)	0	0

For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

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