Stock repurchases (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Apr. 01, 2013
Stock repurchases
Number of shares repurchased and retired under the stock repurchase program	722,000
Value of shares repurchased and retired under the stock repurchase program excluding commissions paid	$ 4,820
Average price under the stock repurchase program (in dollars per share)	$ 6.68
Remaining amount authorized for the share repurchase program		$ 5,180
Maximum
Stock repurchases
Amount of common stock approved by the entity for a stock repurchase program			$ 10,000