Income Taxes	9 Months Ended
Sep. 30, 2019
Income Taxes [Abstract]
Income Taxes	6. Income Taxes We recorded an income tax benefit of $14.9 million and an income tax expense of $9.2 million for the three and nine months ended September 30, 2019, compared to income tax expense of $0.5 million and $0.8 million for the same periods in 2018, respectively. The tax benefit recorded for the three months ended September 30, 2019 varies from what we would have recorded using the U.S. federal statutory rate primarily due to a state tax benefit resulting from our combined state tax filings with Akcea, estimated R&D and orphan drug credits, excess tax benefits related to share-based compensation and a benefit related to a change in the estimated tax value of Akcea shares we received in 2018. The increase in our income tax expense for the nine months ended September 30, 2019, compared to the same period in 2018, was primarily due to our expectation that we will generate U.S. federal and state taxable income in 2019. We expect to utilize our deferred tax assets to partially offset our U.S. federal taxable income.

Income Taxes

9 Months Ended

Sep. 30, 2019

6. Income Taxes

We recorded an income tax benefit of $14.9 million and an income tax expense of $9.2 million for the three and nine months ended September 30, 2019, compared to income tax expense of $0.5 million and $0.8 million for the same periods in 2018, respectively. The tax benefit recorded for the three months ended September 30, 2019 varies from what we would have recorded using the U.S. federal statutory rate primarily due to a state tax benefit resulting from our combined state tax filings with Akcea, estimated R&D and orphan drug credits, excess tax benefits related to share-based compensation and a benefit related to a change in the estimated tax value of Akcea shares we received in 2018. The increase in our income tax expense for the nine months ended September 30, 2019, compared to the same period in 2018, was primarily due to our expectation that we will generate U.S. federal and state taxable income in 2019. We expect to utilize our deferred tax assets to partially offset our U.S. federal taxable income.