Subsequent Events

12 Months Ended

Dec. 31, 2013

Subsequent Events [Abstract]

Subsequent Events [Text Block]

Subsequent Event

On January 28, 2014, the Company entered into a note purchase agreement. The Company contracted to issue $50.0 million and $100.0 million of Senior Notes under the agreement on April 15, 2014 and July 15, 2014, respectively, with due dates ranging from July 2024 to April 2044 at a weighted average interest rate of 4.6 percent.

On December 12, 2013, MDU Energy Capital entered into a note purchase agreement. MDU Energy Capital contracted to issue $30.0 million of Senior Notes under the agreement on January 27, 2014, with due dates ranging from January 2029 to January 2044 at a weighted average interest rate of 5.3 percent.

On February 10, 2014, the Company entered into an agreement to purchase working interests and leasehold positions in oil and natural gas production assets in the southern Powder River Basin of Wyoming for approximately $183.0 million, subject to accounting and purchase price adjustments customary with acquisitions of this type. The effective date of the acquisition is October 1, 2013, with the expected closing date to occur on or before April 1, 2014, conditioned upon completing a due diligence process, including environmental reviews, and satisfying other standard closing conditions.