Commitments and contingencies - Others (Details) $ in Millions |
3 Months Ended | 6 Months Ended |
|---|---|---|
|
Jun. 30, 2020
USD ($)
|
Jun. 30, 2020
USD ($)
|
|
| Commitments and contingencies | ||
| Non-cancellable obligations | $ 7.7 | $ 7.7 |
| 2020 deliverables (remaining six months) | 4.8 | 4.8 |
| 2021 deliverables | 2.9 | 2.9 |
| Licensing fees from intellectual property licenses | $ 0.1 | $ 0.2 |