Income Taxes	3 Months Ended
Mar. 31, 2019
Income Taxes
Income Taxes	10. Income Taxes Our effective income tax rate (ETR) for the three months ended March 31, 2019 and 2018 was 24 percent and 21 percent, respectively. We recognized a loss before income taxes, and a corresponding income tax benefit, for the three months ended March 31, 2019, as a result of the one-time $800 million payment to Arena in January 2019. As a result of this loss, our anticipated tax credits, partially offset by non-deductible compensation expense, increased our tax benefit and resulting ETR for the three months ended March 31, 2019 compared to the three months ended March 31, 2018. Deferred tax assets increased by $169.8 million as of March 31, 2019 compared to December 31, 2018 primarily due to the amount of the Arena payment that will not be deductible for tax purposes in 2019. As of March 31, 2019 and 2018, our unrecognized tax benefits were $0.5 million, and included $0.3 million of tax benefits that, if recognized, would impact our ETR. We record interest and penalties related to uncertain tax positions as a component of income tax expense. As of March 31, 2019 and 2018, we have not accrued any material interest expense related to uncertain tax positions. We are unaware of any material positions for which it is reasonably possible that the total amounts of unrecognized tax benefits will significantly increase or decrease within the next twelve months.

10. Income Taxes

Our effective income tax rate (ETR) for the three months ended March 31, 2019 and 2018 was 24 percent and 21 percent, respectively. We recognized a loss before income taxes, and a corresponding income tax benefit, for the three months ended March 31, 2019, as a result of the one-time $800 million payment to Arena in January 2019. As a result of this loss, our anticipated tax credits, partially offset by non-deductible compensation expense, increased our tax benefit and resulting ETR for the three months ended March 31, 2019 compared to the three months ended March 31, 2018. Deferred tax assets increased by $169.8 million as of March 31, 2019 compared to December 31, 2018 primarily due to the amount of the Arena payment that will not be deductible for tax purposes in 2019.

As of March 31, 2019 and 2018, our unrecognized tax benefits were $0.5 million, and included $0.3 million of tax benefits that, if recognized, would impact our ETR. We record interest and penalties related to uncertain tax positions as a component of income tax expense. As of March 31, 2019 and 2018, we have not accrued any material interest expense related to uncertain tax positions. We are unaware of any material positions for which it is reasonably possible that the total amounts of unrecognized tax benefits will significantly increase or decrease within the next twelve months.