Derivative Instruments - Fair Value of Derivative Instruments Balance Sheet Classification (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands |
Sep. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Current assets - Derivative instruments | ||
| Derivative Assets | ||
| Gross Fair Value Asset/Liability Amounts | $ 1,402 | $ 7,708 |
| Gross Amounts Offset | (1,402) | (6,076) |
| Net Recognized Fair Value Assets/Liabilities | 0 | 1,632 |
| Current liabilities - Derivative instruments | ||
| Derivative Liabilities | ||
| Gross Fair Value Asset/Liability Amounts | 5,835 | 12,127 |
| Gross Amounts Offset | (1,402) | (6,076) |
| Net Recognized Fair Value Assets/Liabilities | $ 4,433 | $ 6,051 |