| ImpactofDerivativesNetInConsolidatedBalanceSheet [Table Text Block] |
| | | | | | | | | | | | | | | | June 30, 2017 | | | Net Presentation | | Gross Presentation | | | Net Assets (Liabilities) Presented in the Consolidated Balance Sheets | Risk management assets—Commodity forward contracts | | Risk management liabilities—Commodity forward contracts | Accounts receivable, net | | | | | | | Derivative positions subject to enforceable master netting arrangements | | $ | — |
| | $ | — |
| | $ | — |
| Derivative positions not subject to enforceable master netting arrangements | | 2,245 |
| | 2,245 |
| | — |
| | | 2,245 |
| | 2,245 |
| | — |
| Deferred charges and other assets, net | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | — |
| | — |
| | — |
| Derivative positions not subject to enforceable master netting
arrangements | | 2,273 |
| | 2,273 |
| | — |
| | | 2,273 |
| | 2,273 |
| | — |
| Accrued liabilities | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | (203 | ) | | 1,062 |
| | (1,265 | ) | Derivative positions not subject to enforceable master netting
arrangements | | (940 | ) | | — |
| | (940 | ) | | | (1,143 | ) | | 1,062 |
| | (2,205 | ) | Other liabilities | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | (1,545 | ) | | 771 |
| | (2,316 | ) | Derivative positions not subject to enforceable master netting
arrangements | | (3,109 | ) | | — |
| | (3,109 | ) | | | (4,654 | ) | | 771 |
| | (5,425 | ) | Risk management assets (liabilities)—Commodity forward contracts | | | | $ | 6,351 |
| | $ | (7,630 | ) |
| | | | | | | | | | | | | | | | December 31, 2016 | | | Net Presentation | | Gross Presentation | | | Net Assets (Liabilities) Presented in the Consolidated Balance Sheets | Risk management assets—Commodity forward contracts | | Risk management liabilities—Commodity forward contracts | Accounts receivable, net | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | $ | 1,498 |
| | $ | 1,636 |
| | $ | (138 | ) | Derivative positions not subject to enforceable master netting
arrangements | | 6,091 |
| | 6,091 |
| | — |
| | | 7,589 |
| | 7,727 |
| | (138 | ) | Deferred charges and other assets, net | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | — |
| | — |
| | — |
| Derivative positions not subject to enforceable master netting
arrangements | | 5,249 |
| | 5,249 |
| | — |
| | | 5,249 |
| | 5,249 |
| | — |
| Accrued liabilities | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | — |
| | — |
| | — |
| Derivative positions not subject to enforceable master netting
arrangements | | (1,349 | ) | | — |
| | (1,349 | ) | | | (1,349 | ) | | — |
| | (1,349 | ) | Other liabilities | | | | | | | Derivative positions subject to enforceable master netting
arrangements | | (436 | ) | | 2,010 |
| | (2,446 | ) | Derivative positions not subject to enforceable master netting
arrangements | | (3,288 | ) | | — |
| | (3,288 | ) | | | (3,724 | ) | | 2,010 |
| | (5,734 | ) | Risk management assets (liabilities)—Commodity forward contracts | | | | $ | 14,986 |
| | $ | (7,221 | ) |
|