CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 514	$ 249
Current portion of revolving and term loan credit agreement, deferred costs	0	67
Noncurrent portion of revolving and term loan credit agreement, deferred costs	$ 0	$ 196
Common stock, shares authorized (in shares)	75,000	75,000
Common stock, shares issued (in shares)	43,578	35,861
Common stock, shares outstanding (in shares)	43,578	35,861
Series B-2
Convertible preferred stock, shares authorized (in shares)	39	39
Convertible preferred stock, shares reserved (in shares)	39	39
Convertible preferred stock, shares issued (in shares)	0	12
Convertible preferred stock, shares outstanding (in shares)	0	12

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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