Income taxes - Reconciliation of Effective Tax Rate (Details) - Her Majesty's Revenue and Customs (HMRC) |
6 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|
Apr. 01, 2017 |
Dec. 31, 2015 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Jun. 30, 2015 |
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| Income taxes | |||||
| UK tax rate | 19.00% | 20.00% | 19.25% | 20.00% | 20.75% |
| Permanent differences relating to reimbursable tax credits | 1.60% | 2.60% | 1.60% | 2.30% | |
| Permanent differences relating to foreign exchange | (8.70%) | 3.40% | |||
| Surrender of R&D expenditures for R&D tax credit refund | (4.50%) | (8.40%) | (5.90%) | (5.50%) | |
| Change in valuation allowances | (10.80%) | (13.50%) | (14.70%) | (20.70%) | |
| Other | 2.60% | (0.60%) | (2.30%) | (1.40%) | |
| Effective income tax rate | 0.20% | (0.60%) | (1.30%) | (1.10%) | |
| 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 foreign exchange. 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 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 current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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://www.xbrl.org/2003/role/presentationRef
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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://www.xbrl.org/2003/role/presentationRef
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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://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- Details
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