Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Allowance for doubtful accounts	$ 994	$ 1,037
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	135,000,000	135,000,000
Common stock issued (in shares)	83,638,895	82,986,244
Common stock outstanding (in shares)	83,426,656	82,774,005
Treasury stock (in shares)	212,239	212,239
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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