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Note 4 - Regulatory Assets and Liabilities - Amount of Regulatory Assets and Liabilities Recorded on Consolidated Balance Sheets (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Regulatory Assets - Current |  | $ 21,650 | $ 17,225
Regulatory Assets - Long -Term |  | 144,138 | 135,257
Regulatory Assets - Total |  | 165,788 | 152,482
Regulatory Assets - Long -Term |  | 144,138 | 135,257
Regulatory Liabilities - Current |  | 7,480 | 738
Regulatory Liabilities - Long -Term |  | 239,906 | 226,469
Regulatory Liabilities, Total |  | 247,386 | 227,207
Net Regulatory Asset Position - Current |  | 14,170 | 16,487
Net Regulatory Asset Position - Long-Term |  | (95,768) | (91,212)
Net Regulatory Asset/(Liability) Position |  | (81,598) | (74,725)
Deferred Income Taxes [Member] |  |  |
Regulatory Liabilities - Current |  | 0 | 0
Regulatory Liabilities - Long -Term |  | 141,707 | 142,779
Regulatory Liabilities, Total |  | 141,707 | 142,779
Accumulated Reserve for Estimated Removal Costs - Net of Salvage [Member] |  |  |
Regulatory Liabilities - Current |  | 0 | 0
Regulatory Liabilities - Long -Term |  | 97,726 | 83,229
Regulatory Liabilities, Total |  | 97,726 | 83,229
Refundable Fuel Clause Adjustment Revenues [Member] |  |  |
Regulatory Liabilities - Current |  | 3,982 | 121
Regulatory Liabilities - Long -Term |  | 0 | 0
Regulatory Liabilities, Total |  | $ 3,982 | $ 121
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 12 months | 12 months
North Dakota Renewable Resource Recovery Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  | $ 1,515 | $ 177
Regulatory Liabilities - Long -Term |  | 0 | 0
Regulatory Liabilities, Total |  | $ 1,515 | $ 177
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 12 months | 12 months
North Dakota Transmission Cost Recovery Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  | $ 700 | $ 60
Regulatory Liabilities - Long -Term |  | 0 | 0
Regulatory Liabilities, Total |  | $ 700 | $ 60
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 12 months | 12 months
Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits [Member] |  |  |
Regulatory Liabilities - Current |  | $ 471 |
Regulatory Liabilities - Long -Term |  | 0 |
Regulatory Liabilities, Total |  | $ 471 |
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 12 months |
Revenue for Rate Case Expenses Subject to Refund - Minnesota [Member] |  |  |
Regulatory Liabilities - Current |  | $ 0 | $ 0
Regulatory Liabilities - Long -Term |  | 401 | 166
Regulatory Liabilities, Total |  | 401 | 166
South Dakota Phase-in Rate Plan Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  | 355 |
Regulatory Liabilities - Long -Term |  | 0 |
Regulatory Liabilities, Total |  | $ 355 |
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 9 months |
MISO Schedule 26/26A Transmission Cost Recovery Rider True-up [Member] |  |  |
Regulatory Liabilities - Current |  |  | 0
Regulatory Liabilities - Long -Term |  |  | 187
Regulatory Liabilities, Total |  |  | $ 187
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  |  | 24 months
North Dakota Generation Cost Recovery Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  | $ 287 |
Regulatory Liabilities - Long -Term |  | 0 |
Regulatory Liabilities, Total |  | $ 287 |
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 6 months |
South Dakota Transmission Cost Recovery Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  |  | $ 168
Regulatory Liabilities - Long -Term |  |  | 0
Regulatory Liabilities, Total |  |  | $ 168
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  |  | 12 months
Minnesota Energy Intensive Trade Exposed Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  | $ 164 |
Regulatory Liabilities - Long -Term |  | 0 |
Regulatory Liabilities, Total |  | $ 164 |
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 12 months |
South Dakota Environmental Cost Recovery Rider Accrued Refund [Member] |  |  |
Regulatory Liabilities - Current |  |  | $ 207
Regulatory Liabilities - Long -Term |  |  | 0
Regulatory Liabilities, Total |  |  | $ 207
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  |  | 12 months
Other [Member] |  |  |
Regulatory Liabilities - Current |  | $ 6 | $ 5
Regulatory Liabilities - Long -Term |  | 72 | 108
Regulatory Liabilities, Total |  | $ 78 | $ 113
Regulatory Liabilities - Remaining Recovery/Refund Period (Month) |  | 168 months | 180 months
Prior Service Costs and Actuarial Losses on Pensions and Other Postretirement Benefits [Member] |  |  |
Regulatory Assets - Current | [1] | $ 9,090 | $ 6,346
Regulatory Assets - Long -Term | [1] | 129,102 | 118,433
Regulatory Assets - Total | [1] | 138,192 | 124,779
Regulatory Assets - Long -Term | [1] | 129,102 | 118,433
Accumulated Asset Retirement Obligation (ARO) Accretion/Depreciation Adjustment [Member] |  |  |
Regulatory Assets - Current | [1] | 0 |
Regulatory Assets - Long -Term | [1] | 7,772 |
Regulatory Assets - Total | [2] | 7,772 |
Regulatory Assets - Long -Term | [1] | 7,772 |
Accumulated ARO Accretion/Depreciation Adjustment [Member] |  |  |
Regulatory Assets - Current | [1] |  | 0
Regulatory Assets - Long -Term | [1] |  | 7,169
Regulatory Assets - Total | [1] |  | 7,169
Regulatory Assets - Long -Term | [1] |  | 7,169
Conservation Improvement Program Costs and Incentives [Member] |  |  |
Regulatory Assets - Current | [2] | 4,024 | 5,995
Regulatory Assets - Long -Term | [2] | 2,844 | 3,285
Regulatory Assets - Total | [2] | 6,868 | 9,280
Regulatory Assets - Long -Term | [2] | $ 2,844 | $ 3,285
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [2] | 21 months | 21 months
Minnesota Transmission Cost Recovery Rider Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [2] | $ 4,208 | $ 444
Regulatory Assets - Long -Term | [2] | 0 | 0
Regulatory Assets - Total | [2] | 4,208 | 444
Regulatory Assets - Long -Term | [2] | $ 0 | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [2] | 12 months | 12 months
MISO Schedule 26/26A Transmission Cost Recovery Rider True-up [Member] |  |  |
Regulatory Assets - Current | [1] | $ 2,033 | $ 240
Regulatory Assets - Long -Term | [1] | 968 | 0
Regulatory Assets - Total | [1] | 3,001 | 240
Regulatory Assets - Long -Term | [1] | $ 968 | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 24 months | 12 months
Nonservice Costs Components of Postretirement Benefits Capitalized for Ratemaking Purposes and Subject to Deferred Recovery [Member] |  |  |
Regulatory Assets - Current | [1] | $ 0 | $ 0
Regulatory Assets - Long -Term | [1] | 1,681 | 986
Regulatory Assets - Total | [1] | 1,681 | 986
Regulatory Assets - Long -Term | [1] | 1,681 | 986
Big Stone II Unrecovered Project Costs - Minnesota [Member] |  |  |
Regulatory Assets - Current | [1] | 715 | 681
Regulatory Assets - Long -Term | [1] | 225 | 947
Regulatory Assets - Total | [1] | 940 | 1,628
Regulatory Assets - Long -Term | [1] | $ 225 | $ 947
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 16 months | 28 months
Debt Reacquisition Premiums [Member] |  |  |
Regulatory Assets - Current | [1] | $ 201 | $ 207
Regulatory Assets - Long -Term | [1] | 548 | 753
Regulatory Assets - Total | [1] | 749 | 960
Regulatory Assets - Long -Term | [1] | $ 548 | $ 753
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 153 months | 165 months
Deferred Marked-to-Market Losses [Member] |  |  |
Regulatory Assets - Current | [1] | $ 743 | $ 1,661
Regulatory Assets - Long -Term | [1] |  | 743
Regulatory Assets - Total | [1] | $ 743 | 2,404
Regulatory Assets - Long -Term | [1] |  | $ 743
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 12 months | 24 months
Big Stone II Unrecovered Project Costs - South Dakota [Member] |  |  |
Regulatory Assets - Current | [1] | $ 144 | $ 100
Regulatory Assets - Long -Term | [1] | 253 | 342
Regulatory Assets - Total | [1] | 397 | 442
Regulatory Assets - Long -Term | [1] | $ 253 | $ 342
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 33 months | 53 months
South Dakota Deferred Rate Case Expenses Subject to Recovery [Member] |  |  |
Regulatory Assets - Current | [1] | $ 138 | $ 178
Regulatory Assets - Long -Term | [1] | 245 | 0
Regulatory Assets - Total | [1] | 383 | 178
Regulatory Assets - Long -Term | [1] | $ 245 | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 34 months | 12 months
North Dakota Deferred Rate Case Expenses Subject to Recovery [Member] |  |  |
Regulatory Assets - Current | [1] | $ 122 | $ 455
Regulatory Assets - Long -Term | [1] | 244 | 0
Regulatory Assets - Total | [1] | 366 | 455
Regulatory Assets - Long -Term | [1] | $ 244 | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 36 months | 12 months
Minnesota SPP Transmission Cost Recovery Tracker [Member] |  |  |
Regulatory Assets - Current | [1] | $ 0 | $ 0
Regulatory Assets - Long -Term | [1] | 202 | 176
Regulatory Assets - Total | [1] | 202 | 176
Regulatory Assets - Long -Term | [1] | 202 | 176
Minnesota Renewable Resource Rider Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [2] | 131 |
Regulatory Assets - Long -Term | [2] | 0 |
Regulatory Assets - Total | [2] | 131 |
Regulatory Assets - Long -Term | [2] | $ 0 |
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 12 months |
Minnesota Renewable Resource Recovery Rider, Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [2] |  | 452
Regulatory Assets - Long -Term | [2] |  | 0
Regulatory Assets - Total | [2] |  | 452
Regulatory Assets - Long -Term | [2] |  | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [2] |  | 12 months
South Dakota Transmission Cost Recovery Rider Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [2] | $ 97 |
Regulatory Assets - Long -Term | [2] | 0 |
Regulatory Assets - Total | [2] | 97 |
Regulatory Assets - Long -Term | [2] | $ 0 |
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [2] | 2 months |
Minnesota Environmental Cost Recovery Rider Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [2] | $ 4 | $ 121
Regulatory Assets - Long -Term | [2] | 0 | 0
Regulatory Assets - Total | [2] | 4 | 121
Regulatory Assets - Long -Term | [2] | $ 0 | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [2] | 12 months | 12 months
Deferred Lease Expenses [Member] |  |  |
Regulatory Assets - Current | [1] | $ 0 |
Regulatory Assets - Long -Term | [1] | 54 |
Regulatory Assets - Total | [1] | 54 |
Regulatory Assets - Long -Term | [1] | $ 54 |
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] | 39 months |
Deferred Income Taxes [Member] |  |  |
Regulatory Assets - Current | [1] |  | $ 0
Regulatory Assets - Long -Term | [1] |  | 2,423
Regulatory Assets - Total | [1] |  | 2,423
Regulatory Assets - Long -Term | [1] |  | 2,423
Minnesota Energy Intensive Trade Exposed Rider Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [1] |  | 328
Regulatory Assets - Long -Term | [1] |  | 0
Regulatory Assets - Total | [1] |  | 328
Regulatory Assets - Long -Term | [1] |  | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [1] |  | 4 months
North Dakota Environmental Cost Recovery Rider Accrued Revenues [Member] |  |  |
Regulatory Assets - Current | [2] |  | $ 17
Regulatory Assets - Long -Term | [2] |  | 0
Regulatory Assets - Total | [2] |  | 17
Regulatory Assets - Long -Term | [2] |  | $ 0
Regulatory Assets - Remaining Recovery/Refund Period (Month) | [2] |  | 12 months
[1] | Costs subject to recovery without a rate of return.
[2] | Amount eligible for recovery under an alternative revenue program which includes an incentive or rate of return.

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- Definition The net amount of all regulatory assets less all regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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- Definition Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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