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Jointly Owned Electric Facilities | 12 Months Ended
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Dec. 31, 2019
Jointly Owned Utility Plant, Net Ownership Amount [Abstract] |
Jointly Owned Electric Facilities | JOINTLY OWNED ELECTRIC FACILITIES The Company has a 15 percent ownership interest in a twin-unit coal-fired generating facility, Colstrip, located in southeastern Montana, and provides financing for its ownership interest in the project. The Company’s share of related fuel costs as well as operating expenses for plant in service are included in the corresponding accounts in the Consolidated Statements of Income. The Company’s share of utility plant in service for Colstrip and accumulated depreciation (inclusive of the ARO assets and accumulated amortization) were as follows as of December 31 (dollars in thousands):
| 2019 |  | 2018
Utility plant in service | $ | 387,860 |  |  | $ | 384,431 |
Accumulated depreciation | (268,637 | ) |  | (261,997 | )
See Note 10 for further discussion of AROs. While the obligations and liabilities with respect to Colstrip are to be shared among the co-owners on a pro-rata basis, many of the environmental liabilities are joint and several under the law, so that if any co-owner failed to pay its share of such liability, the other co-owners (or any one of them) could be required to pay the defaulting co-owner‘s share (or the entire liability).

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