Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes The Company accounts for income taxes under the liability method in accordance with the provisions of ASC Topic 740, Income Taxes. The Company recognizes future tax benefits, such as net operating losses, to the extent those benefits are expected to be realized in future periods. Due to uncertainty surrounding the realization of its deferred tax assets, the Company has recorded a valuation allowance against its net deferred tax assets. The Company experienced a change in ownership as defined under Section 382 of the U.S. Internal Revenue Code (the “Code”) in August 2011. As a result, the future use of its net operating losses and credit equivalents, after giving effect to net unrealized built-in gains, was previously limited, but the limitations associated with the change in ownership in August 2011 ended as of December 31, 2017. All amounts are available for use if the Company generates future taxable income prior to expiration of the net operating losses, which will begin in 2021. The utilization of the net operating loss carryforwards could be limited beyond the Company's generation of taxable income if an additional change in the underlying ownership of the Company's common stock has occurred subsequent to August 2011, resulting in a limitation on the amounts that could be utilized in any given period under Section 382 of the Code. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (the “2017 Tax Act”) which, among other provisions, reduced the corporate income tax rate from 35% to 21% effective January 1, 2018. During the fourth quarter of 2017, the Company revalued its net deferred tax assets using the newly enacted rate, resulting in a reduction of its net deferred tax assets of $33.1 million. The Company also reduced its valuation allowance by $33.1 million, resulting in no income tax expense being recognized as a result of the revaluation. The Company’s estimate of the impacts of the 2017 Tax Act are provisional and are based upon its analysis and interpretations of currently available information. Uncertainties remain regarding the impact of the 2017 Tax Act due to future regulatory and rulemaking processes, prospects of additional corrective or supplemental legislation, and potential trade or other litigation. These uncertainties, along with the Company’s completion of the calculations and potential changes in its initial assumptions as new information becomes available, could cause the actual charge to ultimately differ from the provisional amount recorded in 2017 related to the enactment of the 2017 Tax Act. All provisional amounts recorded by the Company are fully reserved. There were no adjustments in the nine months ended September 30, 2018 to the provisional amount recorded in the fourth quarter of 2017.

9. Income Taxes

The Company accounts for income taxes under the liability method in accordance with the provisions of ASC Topic 740, Income Taxes. The Company recognizes future tax benefits, such as net operating losses, to the extent those benefits are expected to be realized in future periods. Due to uncertainty surrounding the realization of its deferred tax assets, the Company has recorded a valuation allowance against its net deferred tax assets. The Company experienced a change in ownership as defined under Section 382 of the U.S. Internal Revenue Code (the “Code”) in August 2011. As a result, the future use of its net operating losses and credit equivalents, after giving effect to net unrealized built-in gains, was previously limited, but the limitations associated with the change in ownership in August 2011 ended as of December 31, 2017. All amounts are available for use if the Company generates future taxable income prior to expiration of the net operating losses, which will begin in 2021. The utilization of the net operating loss carryforwards could be limited beyond the Company's generation of taxable income if an additional change in the underlying ownership of the Company's common stock has occurred subsequent to August 2011, resulting in a limitation on the amounts that could be utilized in any given period under Section 382 of the Code.

On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (the “2017 Tax Act”) which, among other provisions, reduced the corporate income tax rate from 35% to 21% effective January 1, 2018. During the fourth quarter of 2017, the Company revalued its net deferred tax assets using the newly enacted rate, resulting in a reduction of its net deferred tax assets of $33.1 million. The Company also reduced its valuation allowance by $33.1 million, resulting in no income tax expense being recognized as a result of the revaluation. The Company’s estimate of the impacts of the 2017 Tax Act are provisional and are based upon its analysis and interpretations of currently available information. Uncertainties remain regarding the impact of the 2017 Tax Act due to future regulatory and rulemaking processes, prospects of additional corrective or supplemental legislation, and potential trade or other litigation. These uncertainties, along with the Company’s completion of the calculations and potential changes in its initial assumptions as new information becomes available, could cause the actual charge to ultimately differ from the provisional amount recorded in 2017 related to the enactment of the 2017 Tax Act. All provisional amounts recorded by the Company are fully reserved. There were no adjustments in the nine months ended September 30, 2018 to the provisional amount recorded in the fourth quarter of 2017.