Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Receivables: net of allowance for doubtful accounts	$ 773	$ 830
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	68,000,000	68,000,000
Common stock, shares outstanding (in shares)	48,012,432	47,964,915