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v3.3.1.900

Condensed Statements of Income and Comprehensive Income (Details 2) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Operating revenues | $ 1,062,485 | $ 1,280,500 | $ 986,215 | $ 862,349 | $ 1,048,288 | $ 1,213,203 | $ 952,564 | $ 900,761 | $ 4,191,549 | $ 4,114,816 | $ 3,920,171
Operating expenses | 1,007,092 | 1,170,757 | 940,887 | 818,680 | 973,720 | 1,094,310 | 890,210 | 837,153 | 3,937,416 | 3,795,393 | 3,599,469
Operating income | $ 55,393 | $ 109,743 | $ 45,328 | $ 43,669 | $ 74,568 | $ 118,893 | $ 62,354 | $ 63,608 | 254,133 | 319,423 | 320,702
Other income |  |  |  |  |  |  |  |  | 19,232 | 9,873 | 6,086
Interest expense |  |  |  |  |  |  |  |  | 93,068 | 86,906 | 83,803
Income before income taxes |  |  |  |  |  |  |  |  | 180,297 | 242,390 | 242,985
Income taxes |  |  |  |  |  |  |  |  | 65,603 | 63,227 | 74,294
Earnings (loss) on common stock |  |  |  |  |  |  |  |  | (623,120) | 297,548 | 278,248
Comprehensive income (loss) |  |  |  |  |  |  |  |  | (617,480) | 294,335 | 289,449
MDU Resources Group, Inc. [Member] |  |  |  |  |  |  |  |  |  |  |
Condensed Financial Statements, Captions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  | 556,112 | 628,578 | 549,239
Operating expenses |  |  |  |  |  |  |  |  | 478,198 | 547,820 | 473,917
Operating income |  |  |  |  |  |  |  |  | 77,914 | 80,758 | 75,322
Other income |  |  |  |  |  |  |  |  | 8,318 | 5,271 | 3,709
Interest expense |  |  |  |  |  |  |  |  | 23,562 | 21,055 | 17,386
Income before income taxes |  |  |  |  |  |  |  |  | 62,670 | 64,974 | 61,645
Income taxes |  |  |  |  |  |  |  |  | 15,882 | 16,819 | 13,520
Equity in earnings of subsidiaries from continuing operations |  |  |  |  |  |  |  |  | 103,162 | 134,903 | 120,929
Net income attributable to the Company from continuing operations |  |  |  |  |  |  |  |  | 149,950 | 183,058 | 169,054
Equity in earnings (loss) of subsidiaries from discontinued operations |  |  |  |  |  |  |  |  | (772,385) | 115,175 | 109,879
Dividends declared on preferred stocks |  |  |  |  |  |  |  |  | 685 | 685 | 685
Earnings (loss) on common stock |  |  |  |  |  |  |  |  | (623,120) | 297,548 | 278,248
Comprehensive income (loss) |  |  |  |  |  |  |  |  | $ (617,480) | $ 294,335 | $ 289,449

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