Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company did not record a provision or benefit for income taxes during the three and nine months ended September 30, 2018 and 2017. The Company continues to maintain a full valuation allowance against its net deferred tax assets. As of September 30, 2018, the Company had unrecognized tax benefits of $2.5 million, none of which would currently affect the Company’s effective tax rate if recognized due to the Company’s net deferred tax assets being fully offset by a valuation allowance. The Company does not anticipate that the amount of unrecognized tax benefits relating to tax positions existing at September 30, 2018 will significantly increase or decrease within the next 12 months. There was no interest expense or penalties related to unrecognized tax benefits recorded through September 30, 2018. A number of years may elapse before an uncertain tax position is audited and finally resolved. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, the Company believes that its reserves for income taxes reflect the most likely outcome. The Company adjusts these reserves, as well as the related interest, with consideration of changing facts and circumstances. Settlement of any particular position could require the use of cash. On December 22, 2017, the U.S. government enacted comprehensive tax legislation referred to as the Tax Cuts and Jobs Act, or the Tax Act. The Tax Act significantly revises the future ongoing U.S. corporate income tax by, among other things, lowering the U.S. corporate income tax rates and implementing a territorial tax system. The corporate tax rate was reduced from 35% to 21% for tax years beginning after December 31, 2017 and certain provisions exist on which to allow accelerated expensing of equipment for a portion of 2017 and for future years. These changes primarily impacted the value of the Company’s deferred tax assets with a corresponding offset to valuation allowance, both of which were recognized in the year ended December 31, 2017. The Tax Act also limits the amount of net operating losses that can be used to reduce taxable income to 80% for net operating losses generated for periods beginning after December 31, 2017. Existing net operating losses, arising in years on or before December 31, 2017 are not affected by the Tax Act. The Company has completed a preliminary assessment of the accounting for the income tax effects of the Tax Act, as it relates to its current structure, including provisions that are effective for tax years beginning in 2018. The Company's preliminary assessment is subject to revisions to any additional guidance issued by the U.S. Treasury Department, Internal Revenue Service, FASB, and other standard-setting and regulatory bodies. Adjustments may materially impact the Company's provision for income taxes and the assessment of the accounting for the tax effects of the Tax Act will not extend beyond one year from the enactment date.

Income Taxes

The Company did not record a provision or benefit for income taxes during the three and nine months ended September 30, 2018 and 2017. The Company continues to maintain a full valuation allowance against its net deferred tax assets.

As of September 30, 2018, the Company had unrecognized tax benefits of $2.5 million, none of which would currently affect the Company’s effective tax rate if recognized due to the Company’s net deferred tax assets being fully offset by a valuation allowance. The Company does not anticipate that the amount of unrecognized tax benefits relating to tax positions existing at September 30, 2018 will significantly increase or decrease within the next 12 months. There was no interest expense or penalties related to unrecognized tax benefits recorded through September 30, 2018.

A number of years may elapse before an uncertain tax position is audited and finally resolved. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, the Company believes that its reserves for income taxes reflect the most likely outcome. The Company adjusts these reserves, as well as the related interest, with consideration of changing facts and circumstances. Settlement of any particular position could require the use of cash.

On December 22, 2017, the U.S. government enacted comprehensive tax legislation referred to as the Tax Cuts and Jobs Act, or the Tax Act. The Tax Act significantly revises the future ongoing U.S. corporate income tax by, among other things, lowering the U.S. corporate income tax rates and implementing a territorial tax system. The corporate tax rate was reduced from 35% to 21% for tax years beginning after December 31, 2017 and certain provisions exist on which to allow accelerated expensing of equipment for a portion of 2017 and for future years. These changes primarily impacted the value of the Company’s deferred tax assets with a corresponding offset to valuation allowance, both of which were recognized in the year ended December 31, 2017.

The Tax Act also limits the amount of net operating losses that can be used to reduce taxable income to 80% for net operating losses generated for periods beginning after December 31, 2017. Existing net operating losses, arising in years on or before December 31, 2017 are not affected by the Tax Act. The Company has completed a preliminary assessment of the accounting for the income tax effects of the Tax Act, as it relates to its current structure, including provisions that are effective for tax years beginning in 2018. The Company's preliminary assessment is subject to revisions to any additional guidance issued by the U.S. Treasury Department, Internal Revenue Service, FASB, and other standard-setting and regulatory bodies. Adjustments may materially impact the Company's provision for income taxes and the assessment of the accounting for the tax effects of the Tax Act will not extend beyond one year from the enactment date.