Income taxes (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets And Liabilities [Line Items]
U.S. federal tax loss carry-forward	$ 10,779	$ 8,511
U.S. State tax loss carry-forward	1,498	653
U.S. federal capital loss carry-forward	188	706
U.S. foreign tax credit carry-forward	0	248
Equity-based compensation, fixed assets and other	1,598	1,446
Total deferred tax assets	14,063us-gaap_DeferredTaxAssetsGross	11,564us-gaap_DeferredTaxAssetsGross
Less: valuation allowance	(14,063)	(11,564)
Net deferred tax asset	$ 0us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 0us-gaap_DeferredTaxAssetsLiabilitiesNet

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+ References

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Amount before allocation of valuation allowances of foreign tax asset attributable to deductible capital loss carry forwards.

+ References

No definition available.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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