Condensed Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Other Paid-in Capital	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2023		1,000
Beginning balance at Dec. 31, 2023	$ 448,850	$ 1	$ 136,184	$ 312,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	28,214			28,214
Net transfers from (to) CEHI, LLC and MDU Resources	(12,758)		1,006	(13,764)
Ending balance (in shares) at Mar. 31, 2024		1,000
Ending balance at Mar. 31, 2024	464,306	$ 1	137,190	327,115
Beginning balance (in shares) at Dec. 31, 2023		1,000
Beginning balance at Dec. 31, 2023	448,850	$ 1	136,184	312,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	108,953
Ending balance (in shares) at Sep. 30, 2024		1,000
Ending balance at Sep. 30, 2024	453,303	$ 1	137,947	315,355
Beginning balance (in shares) at Mar. 31, 2024		1,000
Beginning balance at Mar. 31, 2024	464,306	$ 1	137,190	327,115
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	38,972			38,972
Net transfers from (to) CEHI, LLC and MDU Resources	(13,287)		463	(13,750)
Ending balance (in shares) at Jun. 30, 2024		1,000
Ending balance at Jun. 30, 2024	489,991	$ 1	137,653	352,337
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,767			41,767
Net transfers from (to) CEHI, LLC and MDU Resources	(78,455)		294	(78,749)
Ending balance (in shares) at Sep. 30, 2024		1,000
Ending balance at Sep. 30, 2024	$ 453,303	$ 1	137,947	315,355
Beginning balance (in shares) at Dec. 31, 2024	50,980,924	50,980,924
Beginning balance at Dec. 31, 2024	$ 422,612	$ 510	138,130	283,972
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,672			36,672
Stock-based compensation (in shares)		18,304
APIC, Increase for cost recognition for stock-based compensation	915		915
Ending balance (in shares) at Mar. 31, 2025		50,999,228
Ending balance at Mar. 31, 2025	$ 460,199	$ 510	139,045	320,644
Beginning balance (in shares) at Dec. 31, 2024	50,980,924	50,980,924
Beginning balance at Dec. 31, 2024	$ 422,612	$ 510	138,130	283,972
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 146,492
Ending balance (in shares) at Sep. 30, 2025	51,006,575	51,006,575
Ending balance at Sep. 30, 2025	$ 573,046	$ 510	142,072	430,464
Beginning balance (in shares) at Mar. 31, 2025		50,999,228
Beginning balance at Mar. 31, 2025	460,199	$ 510	139,045	320,644
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	52,843			52,843
Stock-based compensation (in shares)		7,347
APIC, Increase for cost recognition for stock-based compensation	1,367		1,367
Ending balance (in shares) at Jun. 30, 2025		51,006,575
Ending balance at Jun. 30, 2025	514,409	$ 510	140,412	373,487
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	56,977			56,977
APIC, Increase for cost recognition for stock-based compensation	$ 1,660		1,660
Ending balance (in shares) at Sep. 30, 2025	51,006,575	51,006,575
Ending balance at Sep. 30, 2025	$ 573,046	$ 510	$ 142,072	$ 430,464