Derivative Instruments and Fair Value Measurements - Summary of Change in Fair Value of Commodity Derivatives (Detail) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | $ 781 | $ 12,755 | $ 5,690 | $ 37,937 |
| Derivatives Not Designated as Hedging Instruments [Member] | ||||
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | 1,541 | 13,051 | (2,583) | 15,008 |
| Derivatives Not Designated as Hedging Instruments [Member] | Unrealized Gain (Loss) on Commodity Derivatives [Member] | ||||
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | 760 | 296 | (8,273) | (22,929) |
| Derivatives Not Designated as Hedging Instruments [Member] | Realized Gain on Commodity Derivatives [Member] | ||||
| Derivatives Fair Value [Line Items] | ||||
| Total gain (loss) on commodity derivatives | $ 781 | $ 12,755 | $ 5,690 | $ 37,937 |