Derivative Financial Instruments - Offsetting of Derivative Assets (Detail) - Zero Cost Collars [Member] $ in Thousands |
Jun. 30, 2017
USD ($)
|
|---|---|
| Derivative [Line Items] | |
| Asset Derivatives, Gross amounts of recognized assets/liabilities | $ 2 |
| Asset Derivatives, Gross amounts offset in the balance sheets | 0 |
| Asset Derivatives, Net amounts of assets/liabilities presented in the balance sheets | 2 |
| Asset Derivatives, Gross amounts not offset in the balance sheets, Financial instruments | 0 |
| Asset Derivatives, Gross amounts not offset in the balance sheets, Cash collateral pledged | 0 |
| Asset Derivatives, Net amount after master netting | $ 2 |