Income taxes (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred Tax Assets And Liabilities [Line Items]
U.S. federal tax loss carry-forward	$ 8,511	$ 6,400
U.S. State tax loss carry-forward	653	224
Foreign tax loss carry-forward	0	15,552
U.S. federal capital loss carry-forward	706	706
U.S. foreign tax credit carry-forward	248	0
Equity-based compensation, fixed assets and other	1,446	255
Total deferred tax assets	11,564	23,137
Less: valuation allowance	(11,564)	(22,917)
Deferred tax liability - warrants	0	(220)
Net deferred tax asset	$ 0	$ 0