Income Taxes	6 Months Ended
Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Tax provisions for interim periods are calculated using an estimate of actual taxable income or loss for the respective period, rather than estimating the Company's annual effective income tax rate, as the Company is currently unable to reliably estimate its income for the full year. For the three and six months ended June 30, 2017, the Company had U.S. taxable income of approximately $7,950 and $19,750, respectively, for which $159 and $395, respectively, in current income tax expense was recognized due to the alternative minimum tax. For the three and six months ended June 30, 2017, the Company recognized $91 and $222, respectively, of current foreign income tax benefit. For the three and six months ended June 30, 2016, the Company had U.S. taxable loss of approximately $7,780 and $17,680, respectively, for which no current income tax benefit was recognized. For the three and six months ended June 30, 2016, the Company recognized $120 and $213, respectively, of current foreign income tax benefit. For the three and six months ended June 30, 2017, the Company recorded deferred tax benefit of $881 and $1,519, respectively. For the three and six months ended June 30, 2016, the Company recorded deferred tax benefit of $471 and $2,659, respectively. The Company's net deferred tax assets, excluding certain deferred tax liabilities totaling $16,266, are offset by a valuation allowance due to the Company's history of net losses combined with an inability to confirm recovery of the tax benefits of the Company's losses and other net deferred tax assets. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. At June 30, 2017, the Company has loss carryforwards for U.S. federal income tax purposes of approximately $248,300 available to offset future taxable income, including approximately $13,400 obtained via the acquisition of GenVec, and federal and state research and development tax credits of approximately $7,700, prior to consideration of annual limitations that may be imposed under Section 382 of the Internal Revenue Code of 1986, as amended. These carryforwards will begin to expire in 2022. The Company's direct foreign subsidiaries have foreign loss carryforwards of approximately $137,000, most of which do not expire.

Income Taxes

Tax provisions for interim periods are calculated using an estimate of actual taxable income or loss for the respective period, rather than estimating the Company's annual effective income tax rate, as the Company is currently unable to reliably estimate its income for the full year. For the three and six months ended June 30, 2017, the Company had U.S. taxable income of approximately $7,950 and $19,750, respectively, for which $159 and $395, respectively, in current income tax expense was recognized due to the alternative minimum tax. For the three and six months ended June 30, 2017, the Company recognized $91 and $222, respectively, of current foreign income tax benefit. For the three and six months ended June 30, 2016, the Company had U.S. taxable loss of approximately $7,780 and $17,680, respectively, for which no current income tax benefit was recognized. For the three and six months ended June 30, 2016, the Company recognized $120 and $213, respectively, of current foreign income tax benefit. For the three and six months ended June 30, 2017, the Company recorded deferred tax benefit of $881 and $1,519, respectively. For the three and six months ended June 30, 2016, the Company recorded deferred tax benefit of $471 and $2,659, respectively. The Company's net deferred tax assets, excluding certain deferred tax liabilities totaling $16,266, are offset by a valuation allowance due to the Company's history of net losses combined with an inability to confirm recovery of the tax benefits of the Company's losses and other net deferred tax assets. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment.

At June 30, 2017, the Company has loss carryforwards for U.S. federal income tax purposes of approximately $248,300 available to offset future taxable income, including approximately $13,400 obtained via the acquisition of GenVec, and federal and state research and development tax credits of approximately $7,700, prior to consideration of annual limitations that may be imposed under Section 382 of the Internal Revenue Code of 1986, as amended. These carryforwards will begin to expire in 2022. The Company's direct foreign subsidiaries have foreign loss carryforwards of approximately $137,000, most of which do not expire.