Derivative Financial Instruments - Offsetting of Derivative Liabilities (Detail) - Zero Cost Collars [Member] - USD ($) $ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Derivative [Line Items] | ||
| Liability Derivatives, Gross amounts of recognized liabilities | $ 123 | $ 40 |
| Liability Derivatives, Gross amounts offset in the balance sheets | 0 | 0 |
| Liability Derivatives, Net amounts of liabilities presented in the balance sheets | 123 | 40 |
| Liability Derivatives, Gross amounts not offset in the balance sheets, Financial instruments | 0 | 0 |
| Liability Derivatives, Gross amounts not offset in the balance sheets, Cash collateral received/ pledged | 0 | 0 |
| Liability Derivatives, Net amount after master netting | $ 123 | $ 40 |