Derivative Instruments - Fair Value of Derivative Instruments Balance Sheet Classification (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Derivative Assets | ||
| Gross Asset/Liability Amounts | $ 8,336 | $ 1,382 |
| Current assets | ||
| Derivative Assets | ||
| Gross Asset/Liability Amounts | 7,148 | 720 |
| Noncurrent assets | ||
| Derivative Assets | ||
| Gross Asset/Liability Amounts | 1,188 | 662 |
| Current liabilities | ||
| Derivative Liabilities | ||
| Gross Asset/Liability Amounts | $ 0 | $ 527 |