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Income Taxes - Reconciliation of statutory to effective income tax rate (Details) | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract] |  |  |
Federal Statutory Rate | 21.00% | 21.00% | 35.00%
Permanent differences | (13.10%) | (25.70%) | 57.50%
State taxes, net of Federal benefit | (0.10%) | 3.50% | (6.60%)
Rate change | (3.50%) | (0.60%) | 370.50%
Foreign earnings taxed at different rates than U.S. | (3.30%) | 11.80% | (40.50%)
Valuation allowance | 72.80% | 81.20% | (401.40%)
Transition tax | 0 | (0.138) | 0
Net operating loss expiration and remeasurement | (66.20%) | (75.80%) | 0.00%
Changes in uncertain tax reserves | 1.20% | (1.40%) | 3.80%
Other | 1.00% | 0.10% | (4.60%)
Effective tax rate | 9.80% | 0.30% | 13.70%

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