Maximum Ratio Of Indebtedness To Net Capital Threshold Percentage

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480657/210-10-S50-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
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Financing Activities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Financing Activities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Jun. 30, 2026	Dec. 31, 2025
Short-Term Debt [Line Items]
Lease Expiration Date	Jun. 30, 2031
Short-Term Debt	$ 100,000	$ 100,000	$ 150,000
NW Corp Term Loan Due 2027
Short-Term Debt [Line Items]
Short-Term Debt	225,000	$ 225,000
Debt Instrument, Maturity Date		Nov. 26, 2027
Maximum Ratio Of Indebtedness To Net Capital Threshold Percentage		65.00%
Term Loan Due 2026-Effective April 11, 2025
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 50,000	$ 50,000
Term Loan Due 2026
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Dec. 31, 2026	Dec. 31, 2026
South Dakota First Mortgage Bonds Due 2036
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150,000	$ 150,000
Long-term Debt, Maturity Date	Jun. 15, 2036	Jun. 15, 2036
Short-Term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.51%	5.51%
South Dakota First Mortgage Bonds Due 2026
Debt Instrument [Line Items]
Long-term Debt, Maturity Date	Jun. 15, 2026	Jun. 15, 2026
Short-Term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.80%	2.80%
Debt Instrument, Repurchased Face Amount	$ 60,000	$ 60,000