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Income Taxes (Details) - USD ($) $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2020 | Mar. 31, 2019 | Jan. 01, 2021 | Dec. 31, 2019
Income Taxes [Abstract] |  |  |  |
Percentage of taxable income that can be offset with federal net operating losses | 100.00% |  |  | 80.00%
Tax benefit related to CARES Act | $ (1,700) |  |  |
Income tax expense (benefit) | $ (3,257) | $ 31,047 |  |
Effective tax rate | 5.28% |  |  |
Federal statutory rate | 21.00% |  |  |
Akcea [Member] |  |  |  |
Income Taxes [Abstract] |  |  |  |
Tax benefit related to CARES Act | $ (1,700) |  |  |
Plan [Member] |  |  |  |
Income Taxes [Abstract] |  |  |  |
Percentage of taxable income that can be offset with federal net operating losses |  |  | 80.00% |

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- Definition Percentage of taxable income that can be offset by federal net operating losses incurred in 2018 and in future years under the Tax Cut and Jobs Act of 2017 and modified by the Coronavirus Aid, Relief, and Economic Security, or CARES, Act. + References No definition available. + Details
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