XML 44 R31.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Comprehensive income (loss) (Tables) | 6 Months Ended
--- | ---
Jun. 30, 2013
Comprehensive income (loss) [Abstract] |
Comprehensive income (loss) | The after-tax changes in the components of accumulated other comprehensive loss as of June 30, 2013, were as follows:
| Net Unrealized Gain (Loss) on Derivative Instruments Qualifying as Hedges | Net Unrealized Gain (Loss) on Available-for-sale Investments | Postretirement Liability Adjustment | Foreign Currency Translation Adjustment | Total Accumulated Other Comprehensive Loss
| (In thousands)
Balance at December 31, 2012 | $ | 6,018 |  | $ | 119 |  | $ | (54,347 | ) | $ | (511 | ) | $ | (48,721 | )
Other comprehensive income (loss) before reclassifications | (5,594 | ) | (187 | ) | — |  | (302 | ) | (6,083 | )
Amounts reclassified from accumulated other comprehensive loss | (3,168 | ) | 79 |  | 1,072 |  | — |  | (2,017 | )
Net current-period other comprehensive income (loss) | (8,762 | ) | (108 | ) | 1,072 |  | (302 | ) | (8,100 | )
Balance at June 30, 2013 | $ | (2,744 | ) | $ | 11 |  | $ | (53,275 | ) | $ | (813 | ) | $ | (56,821 | )
Reclassification out of accumulated other comprehensive income | Reclassifications out of accumulated other comprehensive loss were as follows:
| Three Months Ended | Six Months Ended | Location on Consolidated Statements of Income
| June 30, 2013 | June 30, 2013
| (In thousands) |
Reclassification adjustment for gain (loss) on derivative instruments included in net income |  |  |
Commodity derivative instruments | $ | 1,382 |  | $ | 5,896 |  | Operating revenues
Interest rate derivative instruments | (664 | ) | (780 | ) | Interest expense
| 718 |  | 5,116 |  |
| (322 | ) | (1,948 | ) | Income taxes
| 396 |  | 3,168 |  |
Amortization of postretirement liability losses included in net periodic benefit cost | (967 | ) | (1,934 | ) | (a)
| 543 |  | 862 |  | Income taxes
| (424 | ) | (1,072 | ) |
Reclassification adjustment for loss on available-for-sale investments included in net income | (67 | ) | (121 | ) | Other income
| 23 |  | 42 |  | Income taxes
| (44 | ) | (79 | ) |
Total reclassifications | $ | (72 | ) | $ | 2,017 |  |
(a) Included in net periodic benefit cost (credit). For more information, see Note 17.

X
- Details
Name: | mdu_ComprehensiveIncomeLossAbstract
Namespace Prefix: | mdu_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of information about items reclassified out of accumulated other comprehensive income (loss). + References No definition available. + Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of accumulated other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669686-108580 + Details
Name: | us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration