Derivative Instruments and Fair Value Measurements - Summary of Change in Fair Value of Commodity Derivatives (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2016 |
Jun. 30, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
|
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | $ 1,409 | $ 9,281 | $ 4,909 | $ 25,182 |
| Derivatives Not Designated as Hedging Instruments [Member] | ||||
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | (6,667) | (4,623) | (4,124) | 1,957 |
| Derivatives Not Designated as Hedging Instruments [Member] | Unrealized Loss on Commodity Derivatives [Member] | ||||
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | (8,076) | (13,904) | (9,033) | (23,225) |
| Derivatives Not Designated as Hedging Instruments [Member] | Realized Gain on Commodity Derivatives [Member] | ||||
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | $ 1,409 | $ 9,281 | $ 4,909 | $ 25,182 |