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Expenses by Nature

12 Months Ended

Dec. 31, 2017

Analysis of income and expense [abstract]

Expenses by Nature

Expenses by Nature

Expenses classified by nature are as follows:



Year ended Dec. 31	2017				2016				2015
	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	775		—		755		—		775		—
Coal inventory writedown (recovery)	—		—		(4	)	—		22		—
Purchased power	162		—		143		—		147		—
Mine depreciation	73		—		63		—		59		—
Salaries and benefits	6		248		6		249		5		250
Other operating expenses	—		269		—		240		—		242
Total	1,016		517		963		489		1,008		492