Segment Information (Details) $ in Thousands |
12 Months Ended | |
|---|---|---|
|
Dec. 31, 2017
USD ($)
|
Dec. 31, 2016
USD ($)
|
|
| Segment Reporting Information [Line Items] | ||
| Number of Reportable Segments | 2 | |
| Net book value of long-lived assets | $ 1,809,225 | $ 1,821,101 |
| Dry bulk vessels | ||
| Segment Reporting Information [Line Items] | ||
| Net book value of long-lived assets | 1,278,447 | 1,409,415 |
| Logistics Business | ||
| Segment Reporting Information [Line Items] | ||
| Net book value of long-lived assets | $ 563,887 | $ 544,065 |