Derivative Instruments - Gain (Loss) for Derivative Instruments Not Designated or Qualifying as Hedging Instruments (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Derivative [Line Items] | ||||
| Realized gains (losses) | $ 592 | $ 80 | $ 1,438 | $ 559 |
| Unrealized gains (losses) | 4 | 310 | 3,287 | (1,268) |
| Total | 596 | 390 | 4,725 | (709) |
| Interest rate swap agreements | ||||
| Derivative [Line Items] | ||||
| Realized gains (losses) | 711 | (154) | 1,575 | (894) |
| Unrealized gains (losses) | 13 | 401 | 3,262 | 2 |
| Total | 724 | 247 | 4,837 | (892) |
| Stock purchase warrant | ||||
| Derivative [Line Items] | ||||
| Realized gains (losses) | 0 | 0 | ||
| Unrealized gains (losses) | 0 | (287) | ||
| Total | 0 | (287) | ||
| Time-charter swap agreement | ||||
| Derivative [Line Items] | ||||
| Realized gains (losses) | 0 | 1,106 | ||
| Unrealized gains (losses) | 0 | (875) | ||
| Total | 0 | 231 | ||
| Forward freight agreements | ||||
| Derivative [Line Items] | ||||
| Realized gains (losses) | (119) | 234 | (137) | 347 |
| Unrealized gains (losses) | (9) | (91) | 25 | (108) |
| Total | $ (128) | $ 143 | $ (112) | $ 239 |