Derivative Instruments and Fair Value Measurements - Summary of Change in Fair Value of Commodity Derivatives (Detail) - Derivatives Not Designated as Hedging Instruments [Member] - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Derivatives Fair Value [Line Items] | ||
| Commodity derivative (loss) gain | $ (1,928) | $ 3,444 |
| Net Cash (Payment) Receipt on derivatives Settlements [Member] | ||
| Derivatives Fair Value [Line Items] | ||
| Commodity derivative (loss) gain | (1,531) | (961) |
| Non-Cash Fair Value Gain (Loss) on Derivatives [Member] | ||
| Derivatives Fair Value [Line Items] | ||
| Commodity derivative (loss) gain | $ (397) | $ 4,405 |