Cash and cash equivalents (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Cash and cash equivalents:
Cash	$ 2,622		$ 3,655
Money market accounts	10,894		23,683
Total cash and cash equivalents	13,516	46,648	27,338	58,138
Interest income	$ 48	$ 54