Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,354	$ 1,405
Unamortized discount, current	1,113	1,109
Unamortized discount, noncurrent	$ 2,214	$ 2,381
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	21,443,226	21,489,112
Common stock, shares outstanding (in shares)	21,443,226	21,489,112