Management's Statement: Reclassification (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fuel, purchased power and cost of natural gas sold	$ 71,686	$ 73,544	$ 331,194	$ 413,486
Operations and maintenance	122,759	116,583	365,533	365,116
Operating income	$ 82,234	70,551	$ 302,352	284,683
Scenario, Adjustment
Fuel, purchased power and cost of natural gas sold		500		1,800
Operations and maintenance		(500)		(1,800)
Operating income		$ 0		$ 0

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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