Income tax (expense) benefit - Deferred income taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 70,871	$ 54,220
Tax loss on liquidation of subsidiary	7,846
Equity compensation	1,450	1,025
Non-deductible reserves	57	409
Total deferred tax assets	80,224	55,654
Valuation allowance	(80,087)	(54,114)
Net deferred tax assets	137	1,540
Deferred tax liabilities:
Financial liabilities	80	95
Property, plant and equipment	57	35
Total deferred tax liability	$ 137	130
Deferred tax, net		$ 1,410