Income Taxes	6 Months Ended
Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	11. Income taxes Deferred tax assets and deferred tax liabilities are determined based on temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company does not recognize a tax benefit for uncertain tax positions unless it is more likely than not that the position will be sustained upon examination by tax authorities, including resolution of any related appeals or litigation processes, based on the technical merits of the position. The tax benefit potentially recorded for these positions is measured at the largest amount of cumulative benefit that has greater than a 50 percent likelihood of being realized upon ultimate settlement. Deferred tax assets that do not meet these recognition criteria are not recorded and the Company recognizes a liability for uncertain tax positions that may result in tax payments. If such unrecognized tax benefits were realized and not subject to valuation allowances, the entire amount would impact the tax provision. As of June 30, 2019, the Company’s uncertain tax positions were subject to valuation allowances and the Company has not recorded provisions for income taxes for the three months and six months ended June 30, 2019 and 2018, respectively. The Company recognized a benefit from income taxes of $218,000 for the three and six months ended June 30, 2019 and $0 for the three and six months ended June 30, 2018. The income tax benefit is primarily related to the net unrealized gain on the Company's short term and long-term investments, resulting in an increase in deferred tax liabilities and a decrease in the valuation allowance.

Income Taxes

6 Months Ended

Jun. 30, 2019

11. Income taxes

Deferred tax assets and deferred tax liabilities are determined based on temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized.

The Company does not recognize a tax benefit for uncertain tax positions unless it is more likely than not that the position will be sustained upon examination by tax authorities, including resolution of any related appeals or litigation processes, based on the technical merits of the position. The tax benefit potentially recorded for these positions is measured at the largest amount of cumulative benefit that has greater than a 50 percent likelihood of being realized upon ultimate settlement. Deferred tax assets that do not meet these recognition criteria are not recorded and the Company recognizes a liability for uncertain tax positions that may result in tax payments. If such unrecognized tax benefits were realized and not subject to valuation allowances, the entire amount would impact the tax provision. As of June 30, 2019, the Company’s uncertain tax positions were subject to valuation allowances and the Company has not recorded provisions for income taxes for the three months and six months ended June 30, 2019 and 2018, respectively.

The Company recognized a benefit from income taxes of $218,000 for the three and six months ended June 30, 2019 and $0 for the three and six months ended June 30, 2018. The income tax benefit is primarily related to the net unrealized gain on the Company's short term and long-term investments, resulting in an increase in deferred tax liabilities and a decrease in the valuation allowance.