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Note 3 - Rate and Regulatory Matters - Summary of Revenues Recorded Under Rate Riders (Details) - Otter Tail Power Company [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues recorded under rate riders	$ 7,016	$ 4,537	$ 17,182	$ 11,417
Renewable Resource Adjustment [Member] | Minnesota1 [Member]
Revenues recorded under rate riders	3,088	1,317	6,342	2,633
Renewable Resource Adjustment [Member] | North Dakota 1 [Member]
Revenues recorded under rate riders	1,070	(93)	2,199	636
Conservation Improvement Program Costs and Incentives [Member] | Minnesota1 [Member]
Revenues recorded under rate riders	1,521	1,841	2,607	2,728
Conservation Improvement Program Costs and Incentives [Member] | South Dakota 1 [Member]
Revenues recorded under rate riders	210	96	554	340
Transmission Cost Recovery Rider [Member] | Minnesota1 [Member]
Revenues recorded under rate riders	(314)	(56)	401	585
Transmission Cost Recovery Rider [Member] | North Dakota 1 [Member]
Revenues recorded under rate riders	840	874	2,322	2,646
Transmission Cost Recovery Rider [Member] | South Dakota 1 [Member]
Revenues recorded under rate riders	371	371	933	844
Environmental Cost Recovery Rider [Member] | Minnesota1 [Member]
Revenues recorded under rate riders	0	0	0	(1)
Environmental Cost Recovery Rider [Member] | North Dakota 1 [Member]
Revenues recorded under rate riders	0	(12)	0	563
Environmental Cost Recovery Rider [Member] | South Dakota 1 [Member]
Revenues recorded under rate riders	0	(23)	0	(27)
Generation Cost Recovery [Member] | North Dakota 1 [Member]
Revenues recorded under rate riders	900	222	1,848	470
Phase-In Rate Plan [Member] | South Dakota 1 [Member]
Revenues recorded under rate riders	$ (670)	$ 0	$ (24)	$ 0

X

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

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