Note 1 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Public Utility Property, Plant, and Equipment [Table Text Block]

Jointly Owned Facilities (dollars in thousands)	OTP Ownership Percentage			Electric Plant in Service		Construction Work in Progress			Accumulated Depreciation			Net Plant
December 31, 2019
Big Stone Plant		53.9	%	$	337,197	$	384		$	(98,654	)	$	238,927
Coyote Station		35.0	%		184,493		83			(108,248	)		76,328
Big Stone South–Ellendale 345 kV line1		50.0	%		106,343		-			(819	)		105,524
Fargo–Monticello 345 kV line		14.2	%		78,184		-			(7,011	)		71,173
Big Stone South–Brookings 345 kV line		50.0	%		53,036		-			(2,016	)		51,020
Brookings–Southeast Twin Cities 345 kV line		4.8	%		26,286		-			(2,086	)		24,200
Bemidji–Grand Rapids 230 kV line		14.8	%		16,331		-			(233	)		16,098
December 31, 2018
Big Stone Plant		53.9	%	$	336,051	$	361		$	(92,007	)	$	244,405
Coyote Station		35.0	%		177,713		2,588			(100,997	)		79,304
Big Stone South–Ellendale 345 kV line1		50.0	%		-		106,490			-			106,490
Fargo–Monticello 345 kV line		14.2	%		78,184		-			(5,891	)		72,293
Big Stone South–Brookings 345 kV line		50.0	%		53,235		(150	)		(1,264	)		51,821
Brookings–Southeast Twin Cities 345 kV line		4.8	%		26,281		-			(1,713	)		24,568
Bemidji–Grand Rapids 230 kV line		14.8	%		16,331		-			(2,091	)		14,240

Investment [Table Text Block]

(in thousands)	2019		2018
Cost Method:
Economic Development Loan Pools	$	24	$	34
Other		73		123
Equity Method Partnerships		27		26
Marketable Debt Securities Classified as Available-for-Sale		8,184		7,484
Marketable Equity Securities Classified as Available-for-Sale		1,586		1,294
Total Investments	$	9,894	$	8,961

Schedule of Inventory, Current [Table Text Block]

	December 31,		December 31,
(in thousands)	2019		2018
Finished Goods	$	31,863	$	37,130
Work in Process		16,508		20,393
Raw Material, Fuel and Supplies		49,480		48,747
Total Inventories	$	97,851	$	106,270

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

December 31, 2019 (in thousands)	Level 1		Level 2		Level 3
Assets:
Investments:
Equity Funds – Held by Captive Insurance Company	$	1,586
Corporate Debt Securities – Held by Captive Insurance Company			$	2,124
Government-Backed and Government-Sponsored Enterprises’ Debt Securities – Held by Captive Insurance Company				6,060
Other Assets:
Money Market and Mutual Funds – Retirement Plans		2,363
Total Assets	$	3,949	$	8,184

December 31, 2018 (in thousands)	Level 1		Level 2		Level 3
Assets:
Investments:
Equity Funds – Held by Captive Insurance Company	$	1,294
Corporate Debt Securities – Held by Captive Insurance Company			$	5,898
Government-Backed and Government-Sponsored Enterprises’ Debt Securities – Held by Captive Insurance Company				1,586
Other Assets:
Money Market and Mutual Funds – Nonqualified Retirement Savings Plan		838
Total Assets	$	2,132	$	7,484

Schedule of Goodwill [Table Text Block]

(in thousands)	Gross Balance December 31, 2018		Accumulated Impairments		Balance (net of impairments) December 31, 2018		Adjustments to Goodwill in 2019		Balance (net of impairments) December 31, 2019
Manufacturing	$	18,270	$	-	$	18,270	$	-	$	18,270
Plastics		19,302		-		19,302		-		19,302
Total	$	37,572	$	-	$	37,572	$	-	$	37,572

(in thousands)	Gross Balance December 31, 2017		Accumulated Impairments		Balance (net of impairments) December 31, 2017		Adjustments to Goodwill in 2018		Balance (net of impairments) December 31, 2018
Manufacturing	$	18,270	$	-	$	18,270	$	-	$	18,270
Plastics		19,302		-		19,302		-		19,302
Total	$	37,572	$	-	$	37,572	$	-	$	37,572

Schedule of Finite-Lived Intangible Assets [Table Text Block]

December 31, 2019 (in thousands)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Remaining Amortization Periods (months)
Amortizable Intangible Assets:
Customer Relationships	$	22,491	$	11,259	$	11,232		88 - 188
Other		179		121		58		8 - 45
Total	$	22,670	$	11,380	$	11,290
December 31, 2018 (in thousands)
Amortizable Intangible Assets:
Customer Relationships	$	22,491	$	10,127	$	12,364		12 - 200
Other		154		68		86		20
Total	$	22,645	$	10,195	$	12,450

Finite-lived Intangible Assets Amortization Expense [Table Text Block]

(in thousands)	2019		2018		2017
Amortization Expense – Intangible Assets	$	1,186	$	1,315	$	1,347

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]

(in thousands)	2020		2021		2022		2023		2024
Estimated Amortization Expense – Intangible Assets	$	1,140	$	1,105	$	1,105	$	1,104	$	1,099

Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]

	As of December 31,
(in thousands)	2019		2018
Noncash Investing Activities:
Transactions Related to Capital Additions not Settled in Cash	$	37,429	$	13,757

(in thousands)	2019		2018		2017
Cash Paid During the Year for:
Interest (net of amount capitalized)	$	30,132	$	28,109	$	29,791
Income Taxes	$	4,797	$	6,109	$	5,064

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

(in thousands)	Unrealized Gains on Available-for- Sale Securities		Unamortized Actuarial Losses and Prior Service Costs on Pension and Other Postretirement Benefits			AOCI/(L)
Balance on December 22, 2017 – Pre-tax	$	71	$	(5,672	)	$	(5,601	)
Effect of TCJA 14% Federal Tax Rate Reduction on Gross Deferred Tax Amounts	$	10	$	(794	)	$	(784	)