Earnings (loss) per share (EPS) - Schedule of Diluted Earnings Per Shares Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Basic income (loss) per share
Net income (loss)	$ 3,534	$ (7,596)	$ 5,795	$ (711)	$ (895)
Basic weighted average shares outstanding (in shares)	49,133,000	48,909,000	49,100,000	48,768,000
Basic income (loss) per share (in dollars per share)	$ 0.07	$ (0.16)	$ 0.12	$ (0.01)
Effect of stock options and awards outstanding:
Basic weighted average shares outstanding (in shares)	49,133,000	48,909,000	49,100,000	48,768,000
Effect from dilutive shares and options outstanding (in shares)	826,000	0	769,000	0
Diluted weighted average shares (in shares)	49,959,000	48,909,000	49,869,000	48,768,000
Diluted income (loss) per share (in dollars per share)	$ 0.07	$ (0.16)	$ 0.12	$ (0.01)