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Document And Entity Information - shares | 9 Months Ended |
--- | --- | ---
Sep. 30, 2015 | Oct. 30, 2015
Entity Information [Line Items] |  |
Entity registrant name | MDU RESOURCES GROUP INC |
Entity central index key | 0000067716 |
Current fiscal year end date | --12-31 |
Entity filer category | Large Accelerated Filer |
Entity common stock, shares outstanding |  | 195,265,744
Document fiscal year focus | 2015 |
Document fiscal period focus | Q3 |
Document type | 10-Q |
Amendment flag | false |
Document period end date | Sep. 30, 2015 |

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