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LEASES: | 12 Months Ended
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Dec. 31, 2020
LEASES: |
LEASES: | NOTE 9—LEASES: ​ The Company has operating leases for power generating facilities, vehicles and properties. The Company recognizes lease expense for these leases on a straight-line basis over the lease term. Some of the Company’s leases include both lease and non-lease components which are accounted for separately. The Company’s leases have remaining lease terms of two years to 13 years, and do not include options to extend the leases. The Company’s lease agreements do not contain options to purchase the leased assets or to terminate the leases before the expiration date. In addition, the Company’s lease contracts do not have any material residual value guarantees or material restrictive covenants. As none of the Company’s leases provides an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. ​ The weighted average remaining lease term for the Company’s leases is 9 years, and the weighted average discount rate for these leases is 3.71%. ​ The operating lease expense recognized in the years ended December 31, 2020 and 2019 was classified as follows (in millions): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
Classification |  | 2020 |  | 2019
Cost of sales (exclusive of depreciation, amortization and depletion) |  | $ | 114.4 | ​ | $ | 114.4
Selling, general and administrative | ​ |  | 0.2 | ​ |  | 0.2
Exploration | ​ |  | 0.2 | ​ |  | 0.2
Total lease expense |  | $ | 114.8 | ​ | $ | 114.8
​ The Company’s short-term lease costs for the year ended December 31, 2020 were $0.1 million. ​ Maturities of lease liabilities are as follows: ​
​ | ​ | ​ | ​
​ | ​ | Lease liabilities
Year |  | (in millions)
2021 |  | $ | 114.7
2022 | ​ |  | 113.7
2023 | ​ |  | 112.3
2024 | ​ |  | 104.7
2025 | ​ |  | 103.7
After 2025 | ​ |  | 723.0
Total lease payments |  | $ | 1,272.1
Less: interest on lease liabilities | ​ |  | (293.1)
Present value of lease payments |  | $ | 979.0
​

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- Definition The entire disclosure for operating leases of lessee. Includes, but is not limited to, description of operating lease and maturity analysis of operating lease liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -URI http://asc.fasb.org/subtopic&trid=77888251 + Details
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