Derivative Instruments - Fair Value of Derivative Instruments Balance Sheet Classification (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Derivative Assets | ||
| Gross Asset/Liability Amounts | $ 25,613 | $ 1,382 |
| Derivative Liabilities | ||
| Gross Asset/Liability Amounts | 5,743 | 527 |
| Current assets | ||
| Derivative Assets | ||
| Gross Asset/Liability Amounts | 23,991 | 720 |
| Noncurrent assets | ||
| Derivative Assets | ||
| Gross Asset/Liability Amounts | 1,622 | 662 |
| Current liabilities | ||
| Derivative Liabilities | ||
| Gross Asset/Liability Amounts | 1,264 | 527 |
| Noncurrent liabilities | ||
| Derivative Liabilities | ||
| Gross Asset/Liability Amounts | $ 4,479 | $ 0 |