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Other Commitments and Contingencies Other Commitments and Contingencies (Tables) | 12 Months Ended
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Dec. 31, 2018
Long-term Purchase Commitment [Line Items] |
Long-term Purchase Commitment [Table Text Block] | The total purchase obligations for natural gas, electric and propane supplies are as follows:
Year |  | 2019 |  | 2020-2021 |  | 2022-2023 |  | Beyond 2023 |  | Total
(in thousands) |  |  |  |  |  |  |  |  |  |
Purchase Obligations |  | $ | 158,544 |  |  | $ | 74,970 |  |  | $ | 42,279 |  |  | $ | 129,019 |  |  | $ | 404,812 |

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- Definition Tabular disclosure of key provisions of an arrangement under which the entity has agreed to purchase goods or services over a period of time greater than one year or the normal operating cycle, if longer, including the item for which expenditures will be made, minimum quantities, milestones, time period and committed amount. + References No definition available. + Details
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