| Fair Value Measurements, Recurring and Nonrecurring |
The following tables summarize the carrying amounts, fair values and fair value measurements recorded or disclosed as of December 31, 2017 and 2018, based on the three levels established by ASC 820; Fair Value Measurements and Disclosures (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements as of December 31, 2017 using: | Assets (Liabilities) | | Carrying Amount | | Fair Value | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | Energy commodity derivatives contracts | | $ | (26,085 | ) | | $ | (26,085 | ) | | $ | (26,085 | ) | | $ | — |
| | $ | — |
| Interest rate contracts | | $ | 12,177 |
| | $ | 12,177 |
| | $ | — |
| | $ | 12,177 |
| | $ | — |
| Long-term receivables | | $ | 27,676 |
| | $ | 27,676 |
| | $ | — |
| | $ | — |
| | $ | 27,676 |
| Debt | | $ | (4,524,492 | ) | | $ | (4,826,480 | ) | | $ | — |
| | $ | (4,826,480 | ) | | $ | — |
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements as of December 31, 2018 using: | Assets (Liabilities) | | Carrying Amount | | Fair Value | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | Energy commodity derivatives contracts | | $ | 55,011 |
| | $ | 55,011 |
| | $ | 55,011 |
| | $ | — |
| | $ | — |
| Interest rate contracts | | $ | (8,126 | ) | | $ | (8,126 | ) | | $ | — |
| | $ | (8,126 | ) | | $ | — |
| Long-term receivables | | $ | 20,844 |
| | $ | 20,844 |
| | $ | — |
| | $ | — |
| | $ | 20,844 |
| Guarantees | | $ | (16,409 | ) | | $ | (16,409 | ) | | $ | — |
| | $ | — |
| | $ | (16,409 | ) | Debt | | $ | (4,270,869 | ) | | $ | (4,224,373 | ) | | $ | — |
| | $ | (4,224,373 | ) | | $ | — |
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