Derivative Instruments - Gains and Losses from Derivative Instruments (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Derivative Instruments and Hedging Activities Disclosure [Abstract] | ||||
| Net gain (loss) on derivative instruments | $ 1,522 | $ (9,571) | $ (2,221) | $ 14,969 |