Income taxes - Reconciliation of Effective Tax Rate (Details) - Her Majesty's Revenue and Customs (HMRC) |
12 Months Ended | |||
|---|---|---|---|---|
Apr. 01, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Income taxes | ||||
| UK tax rate | 19.00% | 19.00% | 19.25% | 20.00% |
| Reimbursable tax credits | 3.50% | 2.60% | 1.60% | |
| Surrender of R&D expenditures for R&D tax credit refund | (10.00%) | (8.40%) | (5.90%) | |
| Change in valuation allowances | (17.50%) | (13.50%) | (14.70%) | |
| Difference in tax rates | (1.30%) | (1.40%) | (2.60%) | |
| R&D tax credits generated | 5.10% | 0.70% | ||
| Other | 0.80% | 0.10% | 0.30% | |
| Effective income tax rate | (0.50%) | (0.60%) | (1.30%) | |
| X | ||||||||||
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pre-tax income (loss) from continuing operations attributable to permanent difference relating to reimbursable tax credits. No definition available.
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| X | ||||||||||
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pre-tax income (loss) from continuing operations attributable to the surrender of R&D expenditures for R&D tax credits. No definition available.
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| X | ||||||||||
- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the income tax rates. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to research and development expense. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Details
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