Investment in affiliates and available-for-sale securities - AFS Securities (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
Dec. 31, 2019 |
|
| Schedule Of Equity Method Investments [Line Items] | |||||
| Investment in available-for-sale-securities | $ 153 | $ 153 | $ 189 | ||
| Unrealized loss | $ 36 | ||||
| Unrealized gain | $ 5 | $ 19 | $ 1 | ||