Subsequent events	9 Months Ended
Subsequent events	Sep. 30, 2012
Subsequent Events [Abstract]
Subsequent events	Subsequent events On October 4, 2012, the Company amended its revolving credit agreement to increase the borrowing limit to $125.0 million and extend the termination date to October 4, 2017. MDU Energy Capital entered into a private placement facility and on October 22, 2012, issued $25.0 million of Senior Notes under the agreement, with due dates ranging from October 2022 to October 2042 at a weighted average interest rate of 4.1 percent. MDU Energy Capital intends to issue an additional $25.0 million under the private placement facility on May 15, 2013.

Tabular disclosure of significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, losses resulting from fire or flood, losses on receivables, significant realized and unrealized gains and losses that result from changes in quoted market prices of securities, declines in market prices of inventory, changes in authorized or issued debt (SEC), significant foreign exchange rate changes, substantial loans to insiders or affiliates, significant long-term investments, and substantial dividends not in the ordinary course of business.

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