XML 107 R119.htm IDEA: XBRL DOCUMENT v2.4.0.8

Subsequent Events Subsequent Events (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended			0 Months Ended
	Jul. 15, 2014 MDU Resources Group, Inc [Member]	Apr. 15, 2014 MDU Resources Group, Inc [Member]	Feb. 10, 2014 MDU Resources Group, Inc [Member]	Jan. 27, 2014 MDU Energy Capital [Member]
Subsequent Event [Line Items]
Senior notes issued	$ 100.0	$ 50.0		$ 30.0
Senior notes weighted average interest rate	4.60%	4.60%		5.30%
Purchase Price of Acquisition			$ 183.0

X

- Definition

Purchase price of acquisition subsequent to date of financial statements.

+ References

No definition available.

+ Details

Name:	mdu_PurchasePriceofAcquisition
Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Describes the event or transaction that occurred between the balance sheet date and the date the financial statements are issued or available to be issued.

+ References

No definition available.

+ Details

Name:	mdu_SeniorNotesIssued
Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Describes the event or transaction that occurred between the balance sheet date and the date the financial statements are issued or available to be issued.

+ References

No definition available.

+ Details

Name:	mdu_SeniorNotesWeightedAverageInterestRate
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration