Fair Value Measurements - Recurring Narrative (Detail)
|
3 Months Ended |
|
Mar. 31, 2018
USD ($)
|
|---|
| Commodity derivatives | Level 3 | Minimum |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Forward commodity price |
$ 0.26
|
| Commodity derivatives | Level 3 | Maximum |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Forward commodity price |
$ 1.47
|
| Embedded derivatives in commodity contracts |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Embedded derivative renewal term |
5 years
|
| Embedded derivatives in commodity contracts | Level 3 |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Probability of renewal first term |
62.50%
|
| Probability of renewal second term |
82.00%
|