Derivative financial instruments (Details) - USD ($) $ in Thousands |
6 Months Ended | ||
|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Dec. 31, 2017 |
|
| Breakdown of fair value amount of derivative financial instruments [Abstract] | |||
| Loss on cash flow hedges | $ 33,899 | $ 34,265 | |
| Interest Rate Derivatives [Member] | Cash Flow Hedge [Member] | |||
| Breakdown of fair value amount of derivative financial instruments [Abstract] | |||
| Assets | 13,050 | $ 8,230 | |
| Liabilities | 285,985 | 329,731 | |
| Loss on cash flow hedges | (33,899) | $ (34,265) | |
| After-tax result accumulated in equity | $ 91,935 | $ 80,968 | |