Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes At both September 30, 2020 and 2019, a valuation allowance was recorded against all deferred tax assets due to our cumulative net loss position. We recorded income tax expense of $0.1 million in the three and nine months ended September 30, 2020, compared to $0 in the three and nine months ended September 30, 2019. Income tax expense in the three and nine months ended September 30, 2020 reflects minimal state income tax expense and an accrual for uncertain tax benefits. We filed our 2019 U.S. federal income tax return during the third quarter of 2020. Considering provision to return true-ups, our gross federal net operating loss carryforward as of December 31, 2019 was $165.0 million, which will expire at various dates beginning in 2028. In addition, net operating loss carryforwards for state income tax purposes of $347.1 million that include net operating losses will begin to expire in 2028. We also have gross research and development credit carryforwards of $2.8 million as of December 31, 2019, which will expire at various dates beginning in 2033. Utilization of the net operating loss carryforwards may be subject to an annual limitation due to the ownership change limitations provided by Section 382 of the Internal Revenue Code of 1986 and similar state provisions. We have not performed a detailed analysis to determine whether an ownership change has occurred. Such a change of ownership would limit our utilization of the net operating losses and could be triggered by subsequent sales of securities by us or our stockholders. Realization of the deferred tax assets is dependent upon the generation of future taxable income, if any, the amount and timing of which are uncertain. Based on available objective evidence and cumulative losses, we believe it is more likely than not that the deferred tax assets are not recognizable and will not be recognizable until we have sufficient taxable income. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. We had less than $0.1 million of gross unrecognized tax benefits as of September 30, 2020 and December 31, 2019. We file income tax returns in the applicable jurisdictions. The 2016 to 2019 tax years remain open to examination by the major taxing authorities to which we are subject. We do not expect a significant change to our unrecognized tax benefits over the next 12 months.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.