Subsequent events (Details) - Subsequent Events [Member] - USD ($) $ / shares in Units, $ in Millions |
Nov. 05, 2019 |
Oct. 22, 2019 |
Oct. 08, 2019 |
|---|---|---|---|
| Short term notes [Abstract] | |||
| Short term notes authorized amount | $ 50 | ||
| Short term notes issued amount | $ 25 | ||
| Percentage average cost of issued short term notes | 0.66% | ||
| Dividends approved [Abstract] | |||
| Dividend approved (in dollars per share) | $ 0.41 | ||
| Dividend approved expected date to be paid | Dec. 13, 2019 | ||
| Top of Range [Member] | |||
| Short term notes [Abstract] | |||
| Tenor of short term notes | 2 years | ||
| ATN2 [Member] | |||
| Acquisitions [Abstract] | |||
| Total equity investment | $ 20 | ||
| Required period to obtain authorization for transfer of concession agreement | 8 months |