Notes to Condensed Financial Statements (Details 5) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
2016	$ 243,800,000
2017	51,000,000
2018	175,200,000
2019	119,700,000
Mature in years after 2020	1,260,500,000
MDU Resources Group, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Long-term debt	625,300,000
2016	100,000
2017	100,000
2018	100,100,000
2019	44,600,000
Mature in years after 2020	480,400,000
Cash dividends paid to parent company by consolidated subsidiaries	$ 110,600,000	$ 105,600,000	$ 77,600,000

This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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