XML 31 R64.htm IDEA: XBRL DOCUMENT
v3.20.1

Goodwill rollforward (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 | Mar. 31, 2019 | Dec. 31, 2019
Goodwill [Roll Forward] |  |  |
Balance at beginning of period | $ 681,358 | $ 664,922 | $ 664,922
Goodwill acquired during the year | 32,169 | 14,473 | 23,105
Measurement period adjustments | 0 | 0 | (6,669)
Balance at end of period | 713,527 | 679,395 | 681,358
Natural gas distribution |  |  |
Goodwill [Roll Forward] |  |  |
Balance at beginning of period | 345,736 | 345,736 | 345,736
Goodwill acquired during the year | 0 | 0 | 0
Measurement period adjustments | 0 | 0 | 0
Balance at end of period | 345,736 | 345,736 | 345,736
Construction materials and contracting |  |  |
Goodwill [Roll Forward] |  |  |
Balance at beginning of period | 217,234 | 209,421 | 209,421
Goodwill acquired during the year | 6,483 | 14,473 | 14,482
Measurement period adjustments | 0 | 0 | (6,669)
Balance at end of period | 223,717 | 223,894 | 217,234
Construction services |  |  |
Goodwill [Roll Forward] |  |  |
Balance at beginning of period | 118,388 | 109,765 | 109,765
Goodwill acquired during the year | 25,686 | 0 | 8,623
Measurement period adjustments | 0 | 0 | 0
Balance at end of period | $ 144,074 | $ 109,765 | $ 118,388

X
- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
Name: | us-gaap_Goodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e961-128460 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillPurchaseAccountingAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_GoodwillRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mdu_NaturalGasDistributionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mdu_ConstructionMaterialsAndContractingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mdu_ConstructionServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |