Income Taxes	9 Months Ended
Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 10–Income taxes We estimate our annual effective income tax rate at the end of each quarterly period. This estimate takes into account the mix of expected income or loss before income taxes by tax jurisdiction and enacted changes in tax laws. Our quarterly tax provision and quarterly estimate of the annual effective income tax rate is subject to significant volatility due to several factors, including having to forecast income or loss before income taxes by jurisdiction prior to the completion of the full year, changes in non-deductible expenses or discrete items, as well as the actual amount of income or loss before income taxes. For example, the impact of discrete items on our effective tax rate is greater when income or loss before income taxes is lower. The effective tax rate for the three and nine months ended September 30, 2017, was 17.7% and (20.3%), respectively, compared to 30.7% and (5.0%) for the three and nine months ended September 30, 2016, respectively. The change in the Company's effective tax rate for the three months ended September 30, 2017 compared to the same period in 2016 was primarily due to the impact of discrete items, such as stock option exercises, which generated a tax benefit of $0.5 million, and changes in uncertain tax positions, which generated a tax benefit of $0.5 million. The change in the Company's effective tax rate for the nine months ended September 30, 2017 compared to the same period in 2016 was primarily due to the impact of discrete items, such as stock option exercises, which generated a tax benefit of $4.9 million.

Note 10–Income taxes

We estimate our annual effective income tax rate at the end of each quarterly period. This estimate takes into account the mix of expected income or loss before income taxes by tax jurisdiction and enacted changes in tax laws. Our quarterly tax provision and quarterly estimate of the annual effective income tax rate is subject to significant volatility due to several factors, including having to forecast income or loss before income taxes by jurisdiction prior to the completion of the full year, changes in non-deductible expenses or discrete items, as well as the actual amount of income or loss before income taxes. For example, the impact of discrete items on our effective tax rate is greater when income or loss before income taxes is lower.

The effective tax rate for the three and nine months ended September 30, 2017, was 17.7% and (20.3%), respectively, compared to 30.7% and (5.0%) for the three and nine months ended September 30, 2016, respectively. The change in the Company's effective tax rate for the three months ended September 30, 2017 compared to the same period in 2016 was primarily due to the impact of discrete items, such as stock option exercises, which generated a tax benefit of $0.5 million, and changes in uncertain tax positions, which generated a tax benefit of $0.5 million. The change in the Company's effective tax rate for the nine months ended September 30, 2017 compared to the same period in 2016 was primarily due to the impact of discrete items, such as stock option exercises, which generated a tax benefit of $4.9 million.