Unaudited Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 694	$ 733
Cumulative convertible preferred stock, at par value (in dollars per share)	$ 0.0001	$ 0.0001
Cumulative convertible preferred stock, shares authorized (in shares)	100,000	100,000
Cumulative convertible preferred stock, shares issued (in shares)	0	0
Cumulative convertible preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	80,000,000	80,000,000
Common stock, shares issued (in shares)	61,161,291	60,622,986
Common stock, shares outstanding (in shares)	56,784,694	56,755,293
Treasury stock, shares (in shares)	3,599,267	3,621,435