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Expenses by Nature (Notes)
 12 Months Ended
Dec. 31, 2019
Analysis of income and expense [abstract]  
Expenses by Nature Expenses by Nature
Expenses classified by nature are as follows:
Year ended Dec. 31201920182017
 Fuel and
purchased
power		Operations,
maintenance and
administration		Fuel and
purchased
power		Operations,
maintenance and
administration		Fuel and
purchased
power		Operations,
maintenance and
administration
Fuel(1)
669  —  656  —  685  —  
Purchased power246  —  210  —  162  —  
Mine depreciation119  —  136  —  73  —  
Salaries and benefits(1)
52  228  98  245  96  248  
Other operating expenses—  247  —  270  —  269  
Total1,086  475  1,100  515  1,016  517  
(1) $90 million in 2017 was reclassified from fuel to salaries and benefits to be consistent with the 2018 and 2019 classifications.