Leases - Minimum lease payments (Details) - USD ($) $ in Thousands |
Sep. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Minimum lease payments | ||
| 2019 (three months ending December 31) | $ 3,284 | |
| 2020 | 9,224 | |
| 2021 | 7,551 | |
| 2022 | 7,186 | |
| 2023 | 7,390 | |
| 2024 | 7,601 | |
| Thereafter | 22,058 | |
| Payments due | 64,294 | |
| Less: imputed interest | (15,857) | |
| Operating lease liability | $ 48,437 | |
| Operating Leases, Future Minimum Payments, Due Thereafter | $ 27,777 | |
| Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] | ||
| 2019 | 5,458 | |
| 2020 | 7,141 | |
| 2021 | 7,168 | |
| 2022 | 6,820 | |
| 2023 | 7,024 | |
| Thereafter | 27,777 | |
| Total | $ 61,388 |