Condensed Balance Sheets (Details 3) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 46,107	$ 83,903		$ 60,479		$ 52,566
Receivables, net	630,243	582,475
Inventories	238,273	240,551
Prepayments and other current assets	48,461	29,528
Total current assets	977,475	991,304
Investments	125,866	119,704
Property, plant and equipment	6,510,229	6,387,702
Less accumulated depreciation, depletion and amortization	2,578,902	2,489,322		2,385,202
Net property, plant and equipment	3,931,327	3,898,380		3,520,320
Deferred charges and other assets:
Goodwill	631,791	635,204	[1]	635,204	[1]
Other	415,419	351,603
Total deferred charges and other assets	1,249,799	1,555,766
Total assets	6,284,467	6,565,154		7,805,405
Current liabilities:
Long-term debt due within one year	43,598	238,539
Accounts payable	279,962	286,061
Taxes payable	48,164	46,880
Dividends payable	37,767	36,784
Accrued compensation	65,867	45,192
Other accrued liabilities	184,377	167,322
Total current liabilities	669,659	947,261
Long-term debt	1,746,561	1,557,624
Deferred credits and other liabilities:
Deferred income taxes	668,226	663,629
Other	883,777	812,342
Total deferred credits and other liabilities	1,552,003	1,539,721
Commitments and contingencies (Notes 14, 16 and 17)
Equity:
Preferred stocks	15,000	15,000
Authorized - 500,000,000 shares, $1.00 par value
Issued - 195,843,297 shares in 2016 and 195,804,665 shares in 2015	195,843	195,805
Other paid-in capital	1,232,478	1,230,119
Retained earnings	912,282	996,355
Accumulated other comprehensive loss	(35,733)	(37,148)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)
Total common stockholders' equity	2,301,244	2,381,505
Total stockholders' equity	2,316,244	2,396,505
Total liabilities and equity	$ 6,284,467	$ 6,565,154
Condensed Balance Sheet (Parenthetical)
Common stock, shares authorized	500,000,000	500,000,000
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares issued	195,843,297	195,804,665
Treasury stock, shares	538,921	538,921
MDU Resources Group, Inc. [Member]
Current assets:
Cash and cash equivalents	$ 4,159	$ 2,921		$ 6,120		$ 5,051
Receivables, net	80,467	70,511
Accounts receivable from subsidiaries	34,424	33,129
Inventories	17,352	16,883
Prepayments and other current assets	24,531	7,876
Total current assets	160,933	131,320
Investments	70,370	66,784
Investment in subsidiaries	1,603,874	1,722,351
Property, plant and equipment	2,502,264	2,378,994
Less accumulated depreciation, depletion and amortization	756,191	711,209
Net property, plant and equipment	1,746,073	1,667,785
Deferred charges and other assets:
Goodwill	4,812	4,812
Other	183,654	184,080
Total deferred charges and other assets	188,466	188,892
Total assets	3,769,716	3,777,132
Current liabilities:
Long-term debt due within one year	110	109
Accounts payable	37,697	54,275
Accounts payable to subsidiaries	5,592	6,622
Taxes payable	14,992	10,995
Dividends payable	37,767	36,784
Accrued compensation	16,086	7,539
Other accrued liabilities	34,929	40,931
Total current liabilities	147,173	157,255
Long-term debt	679,667	623,048
Deferred credits and other liabilities:
Deferred income taxes	270,126	255,069
Other	356,506	345,255
Total deferred credits and other liabilities	626,632	600,324
Equity:
Preferred stocks	15,000	15,000
Authorized - 500,000,000 shares, $1.00 par value
Issued - 195,843,297 shares in 2016 and 195,804,665 shares in 2015	195,843	195,805
Other paid-in capital	1,232,478	1,230,119
Retained earnings	912,282	996,355
Accumulated other comprehensive loss	(35,733)	(37,148)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)
Total common stockholders' equity	2,301,244	2,381,505
Total stockholders' equity	2,316,244	2,396,505
Total liabilities and equity	$ 3,769,716	$ 3,777,132
Condensed Balance Sheet (Parenthetical)
Common stock, shares authorized	500,000,000	500,000,000
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares issued	195,843,297	195,804,655
Treasury stock, shares	538,921	538,921

[1] Balance is presented net of accumulated impairment of $12.3 million at the pipeline and midstream segment, which occurred in prior periods.