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Income Taxes - Tax Rate (Details) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Income Tax Disclosure [Abstract] |  |  |
Statutory rate | 21.00% | 21.00% | 21.00%
State taxes | 0.70% | 0.80% | 0.60%
Taxes on foreign earnings | (3.30%) | (4.50%) | (1.90%)
Credits and net operating loss utilization | (1.20%) | (1.10%) | (0.90%)
Purchased intangible assets | 0.70% | 0.40% | 1.20%
Divestiture of Denmark manufacturing operations | (0.40%) | 1.00% | 0.00%
Internal reorganization of certain intellectual property rights | 0.00% | (2.10%) | 0.00%
TECFIDERA impairment | 1.80% | 0.00% | 0.00%
GILTI | 1.30% | 1.50% | 1.60%
U.S. tax reform | 0.00% | 0.00% | 2.10%
Swiss tax reform | 0.00% | (0.80%) | 0.00%
Other | (0.90%) | 0.10% | 0.50%
Effective tax rate | 19.70% | 16.30% | 24.20%

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