Oil and Gas Producing Activities - Schedule of Information Regarding Costs Incurred for Oil and Gas Property Acquisition, Development and Exploration Activities (Parenthetical) (Detail) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Development costs | $ 43,202,000 | $ 15,884,000 | $ 146,237,000 |
| Non-cash Asset Retirement Obligations [Member] | |||
| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Development costs | $ 39,000 | $ 36,000 | $ 151,000 |