Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	5. Income Taxes The Tax Cuts and Jobs Act of 2017 (the 2017 Tax Act), which was signed into law on December 22, 2017, resulted in significant changes to the U.S. corporate income tax system. These changes include a federal statutory rate reduction from 35% to 21% and the elimination or reduction in the deductibility of certain credits and limitations, such as tax credits related to designated orphan drugs, net operating losses, interest expense, and executive compensation. The federal statutory rate reduction took effect on January 1, 2018. The Company’s effective tax rate varies with the statutory rate due primarily to the impact of nondeductible stock-based compensation and the changes in valuation allowance related to certain deferred tax assets generated or utilized in the applicable period. The Company’s deferred tax assets have been fully offset by a valuation allowance at September 30, 2018, and the Company expects to maintain this valuation allowance until there is sufficient evidence that future earnings can be achieved, which is uncertain at this time. On December 22, 2017, Staff Accounting Bulletin No. 118 (SAB 118) was issued to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the 2017 Tax Act. In accordance with SAB 118, the Company continues to evaluate the impact of the 2017 Tax Act, which may impact its current conclusions. Any subsequent adjustment to those amounts will be recorded to current tax expense in the fourth quarter of 2018 when the analysis is expected to be complete. The Internal Revenue Service (IRS) examination team has completed its examination of the Company’s 2013, 2014, and 2015 U.S. tax returns and proposed adjustments with respect to certain items that were reported by the Company for the 2013 tax year. In June 2018, the Company received the Revenue Agent Report from the IRS. The Company believes that it has accurately reported all amounts in its tax returns and has submitted an administrative protest with the IRS contesting the examination team’s proposed adjustments. The Company intends to vigorously defend its reported positions and believes the ultimate resolution of the adjustments proposed by the IRS examination team will not have a material adverse effect on its consolidated financial statements.

5. Income Taxes

The Tax Cuts and Jobs Act of 2017 (the 2017 Tax Act), which was signed into law on December 22, 2017, resulted in significant changes to the U.S. corporate income tax system. These changes include a federal statutory rate reduction from 35% to 21% and the elimination or reduction in the deductibility of certain credits and limitations, such as tax credits related to designated orphan drugs, net operating losses, interest expense, and executive compensation. The federal statutory rate reduction took effect on January 1, 2018.

The Company’s effective tax rate varies with the statutory rate due primarily to the impact of nondeductible stock-based compensation and the changes in valuation allowance related to certain deferred tax assets generated or utilized in the applicable period. The Company’s deferred tax assets have been fully offset by a valuation allowance at September 30, 2018, and the Company expects to maintain this valuation allowance until there is sufficient evidence that future earnings can be achieved, which is uncertain at this time.

On December 22, 2017, Staff Accounting Bulletin No. 118 (SAB 118) was issued to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the 2017 Tax Act. In accordance with SAB 118, the Company continues to evaluate the impact of the 2017 Tax Act, which may impact its current conclusions. Any subsequent adjustment to those amounts will be recorded to current tax expense in the fourth quarter of 2018 when the analysis is expected to be complete.

The Internal Revenue Service (IRS) examination team has completed its examination of the Company’s 2013, 2014, and 2015 U.S. tax returns and proposed adjustments with respect to certain items that were reported by the Company for the 2013 tax year. In June 2018, the Company received the Revenue Agent Report from the IRS. The Company believes that it has accurately reported all amounts in its tax returns and has submitted an administrative protest with the IRS contesting the examination team’s proposed adjustments. The Company intends to vigorously defend its reported positions and believes the ultimate resolution of the adjustments proposed by the IRS examination team will not have a material adverse effect on its consolidated financial statements.