Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 733	$ 664
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)	60,622,986	59,684,669
Common stock, shares outstanding (in shares)	56,755,293	56,972,580
Treasury stock, shares (in shares)	3,621,435	2,028,847