Income Taxes	9 Months Ended
Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes Income tax expense during interim periods is based on applying an estimated annual effective income tax rate to year-to-date income, plus any significant unusual or infrequently occurring items that are recorded in the interim period. The computation of the annual estimated effective tax rate at each interim period requires certain estimates and significant judgment including, but not limited to, the expected operating income for the year, projections of the proportion of income earned and taxed in various jurisdictions, permanent and temporary differences, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, more experience is obtained, additional information becomes known, or as the tax environment changes. The interim financial statement provision for income taxes expense is different from the amounts computed by applying the United States federal statutory income tax rate of 34%. The Company’s effective tax rate (ETR) was -0.2%, -0.2%, -0.2%, and -0.2% for the three and nine months ended September 30, 2017 and 2016, respectively. The difference between the effective tax rate and the federal statutory rate of 34% was primarily due to the full valuation allowance recorded on the Company’s net deferred tax assets and foreign withholding taxes. As of September 30, 2017, there have been no material changes to the Company’s uncertain tax positions.

10. Income Taxes

Income tax expense during interim periods is based on applying an estimated annual effective income tax rate to year-to-date income, plus any significant unusual or infrequently occurring items that are recorded in the interim period. The computation of the annual estimated effective tax rate at each interim period requires certain estimates and significant judgment including, but not limited to, the expected operating income for the year, projections of the proportion of income earned and taxed in various jurisdictions, permanent and temporary differences, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, more experience is obtained, additional information becomes known, or as the tax environment changes.

The interim financial statement provision for income taxes expense is different from the amounts computed by applying the United States federal statutory income tax rate of 34%. The Company’s effective tax rate (ETR) was -0.2%, -0.2%, -0.2%, and -0.2% for the three and nine months ended September 30, 2017 and 2016, respectively. The difference between the effective tax rate and the federal statutory rate of 34% was primarily due to the full valuation allowance recorded on the Company’s net deferred tax assets and foreign withholding taxes.

As of September 30, 2017, there have been no material changes to the Company’s uncertain tax positions.