| Accounts Receivable, Net |
| | | | | | | | | | (Thousands of Dollars) | | Sept. 30, 2017 | | Dec. 31, 2016 | Accounts receivable, net | | | | | Accounts receivable | | $ | 103,704 |
| | $ | 80,569 |
| Less allowance for bad debts | | (7,090 | ) | | (6,379 | ) | | | $ | 96,614 |
| | $ | 74,190 |
|
|
| Inventories |
| | | | | | | | | | (Thousands of Dollars) | | Sept. 30, 2017 | | Dec. 31, 2016 | Inventories | | | | | Materials and supplies | | $ | 26,877 |
| | $ | 25,453 |
| Fuel | | 14,473 |
| | 13,052 |
| | | $ | 41,350 |
| | $ | 38,505 |
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|
| Property, Plant and Equipment, Net |
| | | | | | | | | | (Thousands of Dollars) | | Sept. 30, 2017 | | Dec. 31, 2016 | Property, plant and equipment, net | | | | | Electric plant | | $ | 6,653,228 |
| | $ | 6,362,189 |
| Construction work in progress | | 312,445 |
| | 260,327 |
| Total property, plant and equipment | | 6,965,673 |
| | 6,622,516 |
| Less accumulated depreciation | | (2,018,559 | ) | | (1,926,697 | ) | | | $ | 4,947,114 |
| | $ | 4,695,819 |
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