MDU Resources (MDU) 10-K 17 Feb 10 2009 FY Annual report Financial data

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (USD $)
In Thousands, except Share data	12 Months Ended Dec. 31, 2009	12 Months Ended Dec. 31, 2008	12 Months Ended Dec. 31, 2007
Operating revenues:
Electric, natural gas distribution and pipeline and energy services	$1,504,269	$1,685,199	$1,095,709
Construction services, natural gas and oil production, construction materials and contracting, and other	2,672,232	3,318,079	3,152,187
Total operating revenues	4,176,501	5,003,278	4,247,896
Operating expenses:
Fuel and purchased power	65,717	75,333	69,616
Purchased natural gas sold	739,678	765,900	377,404
Operation and maintenance:
Electric, natural gas distribution and pipeline and energy services	263,869	262,053	215,587
Construction services, natural gas and oil production, construction materials and contracting, and other	2,143,195	2,686,055	2,572,864
Depreciation, depletion and amortization	330,542	366,020	301,932
Taxes, other than income	166,597	200,080	153,373
Write-down of natural gas and oil properties (Note 1)	620,000	135,800	0
Total operating expenses	4,329,598	4,491,241	3,690,776
Operating Income (loss)	(153,097)	512,037	557,120
Earnings from equity method investments	8,499	6,627	19,609
Other income	9,331	4,012	8,318
Interest expense	84,099	81,527	72,237
Income (loss) before income taxes	(219,366)	441,149	512,810
Income taxes	(96,092)	147,476	190,024
Income (loss) from continuing operations	(123,274)	293,673	322,786
Income from discontinued operations, net of tax (Note 3)	0	0	109,334
Net income (loss)	(123,274)	293,673	432,120
Dividends on preferred stocks	(685)	(685)	(685)
Earnings (loss) on common stock	($123,959)	$292,988	$431,435
Earnings (loss) per common share - basic:
Earnings (loss) before discontinued operations	-0.67	1.6	1.77
Discontinued operations, net of tax	$0	$0	0.6
Earnings (loss) per common share - basic	-0.67	1.6	2.37
Earnings (loss) per common share - diluted:
Earnings (loss) before discontinued operations	-0.67	1.59	1.76
Discontinued operations, net of tax	$0	$0	0.6
Earnings (loss) per common share - diluted	-0.67	1.59	2.36
Dividends per common share	0.6225	0.6	0.56
Weighted average common shares outstanding - basic	185,175	183,100	181,946
Weighted average common shares outstanding - diluted	185,175	183,807	182,902

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)
In Thousands	Dec. 31, 2009	Dec. 31, 2008
Current assets:
Cash and cash equivalents	$175,114	$51,714
Receivables, net	531,980	707,109
Inventories	249,804	261,524
Deferred income taxes	28,145	0
Short-term investments	2,833	2,467
Commodity derivative instruments	7,761	78,164
Prepayments and other current assets	66,021	171,314
Total current assets	1,061,658	1,272,292
Investments	145,416	114,290
Property, plant and equipment (Note 1)	6,766,582	7,062,237
Less accumulated depreciation, depletion and amortization	2,872,465	2,761,319
Net property, plant and equipment	3,894,117	4,300,918
Deferred charges and other assets:
Goodwill (Note 5)	629,463	615,735
Other intangible assets, net (Note 5)	28,977	28,392
Other	231,321	256,218
Total deferred charges and other assets	889,761	900,345
Total assets	5,990,952	6,587,845
Current Liabilities:
Short-term borrowings (Note 9)	10,300	105,100
Long-term debt due within one year	12,629	78,666
Accounts payable	281,906	432,358
Taxes payable	55,540	49,784
Deferred income taxes	0	20,344
Dividends payable	29,749	28,640
Accrued compensation	47,425	55,646
Commodity derivative instruments	36,907	56,529
Other accrued liabilities	192,729	140,408
Total current liabilities	667,185	967,475
Long-term debt (Note 9)	1,486,677	1,568,636
Deferred credits and other liabilities:
Deferred income taxes	590,968	727,857
Other liabilities	674,475	562,801
Total deferred credits and other liabilities	1,265,443	1,290,658
Stockholders' equity
Preferred stocks (Note 11)	15,000	15,000
Common stockholders' equity:
Common stock (Note 12) Authorized - 500,000,000 shares, $1.00 par value Issued - 188,389,265 shares in 2009 and 184,208,283 shares in 2008	188,389	184,208
Other paid-in capital	1,015,678	938,299
Retained earnings	1,377,039	1,616,830
Accumulated other comprehensive income (loss)	(20,833)	10,365
Treasury stock at cost – 538,921 shares	(3,626)	(3,626)
Total common stockholders' equity	2,556,647	2,746,076
Total stockholders' equity	2,571,647	2,761,076
Total liabilities and stockholders' equity	$5,990,952	$6,587,845

PARENTHETICAL DATA TO THE CONSO

PARENTHETICAL DATA TO THE CONSOLIDATED BALANCE SHEETS (USD $)
	Dec. 31, 2009	Dec. 31, 2008
Common stockholders' equity:
Common stock par value	1	1
Common stock shares issued	188,389,265	184,208,283
Common stock authorized	500,000,000	500,000,000
Treasury shares	538,921	538,921

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)
In Thousands	12 Months Ended Dec. 31, 2009	12 Months Ended Dec. 31, 2008	12 Months Ended Dec. 31, 2007
Operating activities:
Net income (loss)	($123,274)	$293,673	$432,120
Income from discontinued operations, net of tax (Note 3)	0	0	109,334
Income (loss) from continuing operations	(123,274)	293,673	322,786
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	330,542	366,020	301,932
Earnings, net of distributions, from equity method investments	(3,018)	365	(14,031)
Deferred income taxes	(169,764)	64,890	67,272
Write-down of natural gas and oil properties (Note 1)	620,000	135,800	0
Changes in current assets and liabilities, net of acquisitions:
Receivables	132,939	27,165	(40,256)
Inventories	13,969	(18,574)	(7,130)
Other current assets	67,803	(64,771)	(7,356)
Accounts payable	(61,867)	28,205	24,702
Other current liabilities	44,039	(38,738)	(22,932)
Other noncurrent changes	(4,683)	(7,848)	9,594
Net cash provided by continuing operations	846,686	786,187	634,581
Net cash used in discontinued operations	0	0	(71,389)
Net cash provided by operating activities	846,686	786,187	563,192
Investing activities:
Capital expenditures	(448,675)	(746,478)	(558,283)
Acquisitions, net of cash acquired	(6,410)	(533,543)	(348,490)
Net proceeds from sale or disposition of property	26,679	86,927	24,983
Investments	(3,740)	85,773	(67,140)
Proceeds from sale of equity method investments	0	0	58,450
Net cash used in continuing operations	(432,146)	(1,107,321)	(890,480)
Net cash provided by discontinued operations	0	0	548,216
Net cash used in investing activities	(432,146)	(1,107,321)	(342,264)
Financing activities:
Issuance of short-term borrowings	10,300	216,400	311,700
Repayment of short-term borrowings	(105,100)	(113,000)	(310,000)
Issuance of long-term debt	145,000	453,929	120,250
Repayment of long-term debt	(292,907)	(200,527)	(232,464)
Proceeds from issuance of common stock	65,207	15,011	17,263
Dividends paid	(115,023)	(108,591)	(100,641)
Tax benefit on stock-based compensation	601	4,441	5,398
Net cash provided by (used in) continuing operations	(291,922)	267,663	(188,494)
Net cash provided by discontinued operations	0	0	0
Net cash provided by (used in) financing activities	(291,922)	267,663	(188,494)
Effect of exchange rate changes on cash and cash equivalents	782	(635)	308
Increase (decrease) in cash and cash equivalents	123,400	(54,106)	32,742
Cash and cash equivalents -- beginning of year	51,714	105,820	73,078
Cash and cash equivalents -- end of year	$175,114	$51,714	$105,820

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (USD $)
In Thousands, except Share data	Common Stock	Other Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total
Balance - Amount at Dec. 31, 2006	$181,558	$874,253	$1,104,210	($6,482)	($3,626)	$2,149,913
Balance - Shares at Dec. 31, 2006	181,557,543				(538,921)
Net income (loss)	0	0	432,120	0	0	432,120
Other comprehensive income (loss), net of tax - Net unrealized gain (loss) on derivative instruments qualifying as hedges	0	0	0	(13,505)	0	(13,505)
Postretirement liability adjustment	0	0	0	3,012	0	3,012
Foreign currency translation adjustment	0	0	0	7,177	0	7,177
Net unrealized gain on available-for-sale investments	0	0	0	405	0	405
Total comprehensive income (loss)	0	0	0	0	0	429,209
Uncertain tax positions transition adjustment	0	0	31	0	0	31
Dividends on preferred stock	0	0	(685)	0	0	(685)
Dividends on common stock	0	0	(102,091)	0	0	(102,091)
Tax benefit on stock-based compensation	0	5,398	0	0	0	5,398
Issuance of common stock, shares	1,388,985
Issuance of common stock, amount	1,389	33,155	0	0	0	34,544
Balance - Shares at Dec. 31, 2007	182,946,528				(538,921)
Balance - Amount at Dec. 31, 2007	182,947	912,806	1,433,585	(9,393)	(3,626)	2,516,319
Net income (loss)	0	0	293,673	0	0	293,673
Other comprehensive income (loss), net of tax - Net unrealized gain (loss) on derivative instruments qualifying as hedges	0	0	0	43,448	0	43,448
Postretirement liability adjustment	0	0	0	(13,751)	0	(13,751)
Foreign currency translation adjustment	0	0	0	(9,534)	0	(9,534)
Total comprehensive income (loss)	0	0	0	0	0	313,836
Fair value option transition adjustment	0	0	405	(405)	0	0
Dividends on preferred stock	0	0	(685)	0	0	(685)
Dividends on common stock	0	0	(110,148)	0	0	(110,148)
Tax benefit on stock-based compensation	0	4,441	0	0	0	4,441
Issuance of common stock, shares	1,261,755
Issuance of common stock, amount	1,261	21,052	0	0	0	22,313
Balance - Shares at Dec. 31, 2008	184,208,283				(538,921)
Balance - Amount at Dec. 31, 2008	184,208	938,299	1,616,830	10,365	(3,626)	2,746,076
Net income (loss)	0	0	(123,274)	0	0	(123,274)
Other comprehensive income (loss), net of tax - Net unrealized gain (loss) on derivative instruments qualifying as hedges	0	0	0	(51,684)	0	(51,684)
Postretirement liability adjustment	0	0	0	9,918	0	9,918
Foreign currency translation adjustment	0	0	0	10,568	0	10,568
Total comprehensive income (loss)	0	0	0	0	0	(154,472)
Dividends on preferred stock	0	0	(685)	0	0	(685)
Dividends on common stock	0	0	(115,832)	0	0	(115,832)
Tax benefit on stock-based compensation	0	(117)	0	0	0	(117)
Issuance of common stock, shares	4,180,982
Issuance of common stock, amount	4,181	77,496	0	0	0	81,677
Balance - Shares at Dec. 31, 2009	188,389,265				(538,921)
Balance - Amount at Dec. 31, 2009	$188,389	$1,015,678	$1,377,039	($20,833)	($3,626)	$2,556,647

NOTE 1: SUMMARY OF SIGNIFICANT

NOTE 1: SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Summary Of Significant Accounting Policies	Note1 Summary of Significant Accounting Policies Basis of presentation The consolidated financial statements of the Company include the accounts of the following businesses: electric, natural gas distribution, construction services, pipeline and energy services, natural gas and oil production, construction materials and contracting, and other. The electric, natural gas distribution, and pipeline and energy services businesses are substantially all regulated. Construction services, natural gas and oil production, construction materials and contracting, and other are nonregulated. For further descriptions of the Company's businesses, see Note15. The statements also include the ownership interests in the assets, liabilities and expenses of jointly owned electric generating facilities. The Company's regulated businesses are subject to various state and federal agency regulations. The accounting policies followed by these businesses are generally subject to the Uniform System of Accounts of the FERC. These accounting policies differ in some respects from those used by the Company's nonregulated businesses. The Company's regulated businesses account for certain income and expense items under the provisions of regulatory accounting, which requires these businesses to defer as regulatory assets or liabilities certain items that would have otherwise been reflected as expense or income, respectively, based on the expected regulatory treatment in future rates. The expected recovery or flowback of these deferred items generally is based on specific ratemaking decisions or precedent for each item. Regulatory assets and liabilities are being amortized consistently with the regulatory treatment established by the FERC and the applicable state public service commissions. See Note6 for more information regarding the nature and amounts of these regulatory deferrals. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses. Cash and cash equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Allowance for doubtful accounts The Company's allowance for doubtful accounts as of December31, 2009 and 2008, was $16.6million and $13.7million, respectively. Natural gas in storage Natural gas in storage for the Company's regulated operations is generally carried at average cost, or cost using the last-in, first-out method. The portion of the cost of natural gas in storage expected to be used within one year was included in inventories and was $35.6million and $27.6million at December31, 2009 and 2008, respectively. The remainder of natural gas in storage, which largely represents the cost of the gas required to maintain pressure levels for normal operating purposes, was included in other assets and was $59.6million and $43.4million at December31, 2009 and 2008, respectively. Inventories Inventories, other than natural gas in storage for the Company's regulated operations, consisted primarily of aggregates held fo

NOTE 2: ACQUISITIONS

NOTE 2: ACQUISITIONS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Acquisitions	Note2 Acquisitions In 2009, the Company acquired a pipeline and energy services business in Montana which was not material. The total purchase consideration for this business and purchase price adjustments with respect to certain other acquisitions made prior to 2009, consisting of the Companys common stock and cash, was $22.0million. In 2008, the Company acquired a construction services business in Nevada; natural gas properties in Texas; construction materials and contracting businesses in Alaska, California, Idaho and Texas; and Intermountain, a natural gas distribution business, as discussed below. The total purchase consideration for these businesses and properties and purchase price adjustments with respect to certain other acquisitions made prior to 2008, consisting of the Companys common stock and cash and the outstanding indebtedness of Intermountain, was $624.5million. On October 1, 2008, the acquisition of Intermountain was finalized and Intermountain became an indirect wholly owned subsidiary of the Company. Intermountains service area is in Idaho. In 2007, the Company acquired construction materials and contracting businesses in North Dakota, Texas and Wyoming; a construction services business in Nevada; and Cascade, a natural gas distribution business, as discussed below. The total purchase consideration for these businesses and properties and purchase price adjustments with respect to certain other acquisitions made prior to 2007, consisting of the Company's common stock and cash and the outstanding indebtedness of Cascade, was $526.3million. On July2, 2007, the acquisition of Cascade was finalized and Cascade became an indirect wholly owned subsidiary of the Company. Cascade's natural gas service areas are in Washington and Oregon. The above acquisitions were accounted for under the purchase method of accounting and, accordingly, the acquired assets and liabilities assumed have been preliminarily recorded at their respective fair values as of the date of acquisition. On the above acquisition made in 2009, a final fair market value is pending the completion of the review of the relevant assets and liabilities as of the acquisition date. The results of operations of the acquired businesses and properties are included in the financial statements since the date of each acquisition. Pro forma financial amounts reflecting the effects of the above acquisitions are not presented, as such acquisitions were not material to the Company's financial position or results of operations.

NOTE 3: DISCONTINUED OPERATIONS

NOTE 3: DISCONTINUED OPERATIONS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Discontinued Operations	Note3 Discontinued Operations Innovatum, a component of the pipeline and energy services segment, specialized in cable and pipeline magnetization and location. During the third quarter of 2006, the Company initiated a plan to sell Innovatum because the Company determined that Innovatum is a non-strategic asset. During the fourth quarter of 2006, the stock and a portion of the assets of Innovatum were sold and the Company sold the remaining assets of Innovatum in January2008. The loss on disposal of Innovatum was not material. During the fourth quarter of 2006, the Company initiated a plan to sell certain of the domestic assets of Centennial Resources. The plan to sell was based on the increased market demand for independent power production assets, combined with the Company's desire to efficiently fund future capital needs. The Company subsequently committed to a plan to sell CEM due to strong interest in the operations of CEM during the bidding process for the domestic independent power production assets in the first quarter of 2007. In July 2007, Centennial Resources sold its domestic independent power production business consisting of Centennial Power and CEM to Bicent Power LLC (formerly known as Montana Acquisition Company LLC). The transaction was valued at $636million, which included the assumption of approximately $36million of project-related debt. The gain on the sale of the assets, excluding the gain on the sale of Hartwell as discussed in Note4, was approximately $85.4million (after tax). The Company's consolidated financial statements and accompanying notes for prior periods present the results of operations of Innovatum and the domestic independent power production assets as discontinued operations. In addition, the assets and liabilities of these operations were treated as held for sale, and as a result, no depreciation, depletion and amortization expense was recorded from the time each of the assets was classified as held for sale. Operating results related to Innovatum for the year ended December31, 2007, were as follows: 2007 (In thousands) Operating revenues $ 1,748 Loss from discontinued operations before income tax benefit (210 ) Income tax benefit (316 ) Income from discontinued operations, net of tax $ 106 Operating results related to the domestic independent power production assets for the year ended December31, 2007, were as follows: 2007 (In thousands) Operating revenues $ 125,867 Income from discontinued operations (including gain on disposal in 2007 of $142.4million) before income tax expense 177,666 Income tax expense 68,438 Income from discontinued operations, net of tax $ 109,228 Revenues at the former independent power production operations were recognized based on electricity delivered and capacity provided, pursuant to contractual commitments and, where applicable, revenues were recognized ratably over the terms of the related contract. Arrangements with multiple revenue-generating activities were recognized with the multiple deliverables divided into separate units of accounting based on sp

NOTE 4: EQUITY METHOD INVESTMEN

NOTE 4: EQUITY METHOD INVESTMENTS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Equity Method Investments	Note4 Equity Method Investments Investments in companies in which the Company has the ability to exercise significant influence over operating and financial policies are accounted for using the equity method. The Company's equity method investments at December31, 2009 and 2008, include the Brazilian Transmission Lines. In August2006, MDU Brasil acquired ownership interests in companies owning the Brazilian Transmission Lines. The interests involve the ENTE (13.3-percent ownership interest), ERTE (13.3-percent ownership interest) and ECTE (25-percent ownership interest) electric transmission lines, which are primarily in northeastern and southern Brazil. The transmission contracts provide for revenues denominated in the Brazilian Real, annual inflation adjustments and change in tax law adjustments and have between 21 and 23 years remaining under the contracts. Alusa and CEMIG hold the remaining ownership interests, with CELESC also having an ownership interest in ECTE. The functional currency for the Brazilian Transmission Lines is the Brazilian Real. In the fourth quarter of 2009, multiple sales agreements were signed with three separate parties for the Company to sell its ownership interests in the Brazilian Transmission Lines. This sale is pending regulatory approvals. One of the parties will purchase 15.6percent of the Companys ownership interests over a four-year period. The other parties will purchase 84.4 percent of the Companys ownership interests at the financial close of the transaction. In September 2004, Centennial Resources, through indirect wholly owned subsidiaries, acquired a 50 percent ownership interest in Hartwell, which owns a 310-MW natural gas-fired electric generating facility near Hartwell, Georgia. In July 2007, the Company sold its ownership interest in Hartwell, and realized a gain of $10.1million ($6.1million after tax) from the sale which is recorded in earnings from equity method investments on the Consolidated Statements of Income. At December31, 2009 and 2008, the investments in which the Company held an equity method interest had total assets of $387.0 million and $294.7million, respectively, and long-term debt of $176.7 million and $158.0million, respectively. The Company's investment in its equity method investments was approximately $62.4million and $44.4million, including undistributed earnings of $9.3 million and $6.8million, at December31, 2009 and 2008, respectively.

NOTE 5: GOODWILL AND OTHER INTA

NOTE 5: GOODWILL AND OTHER INTANGIBLE ASSETS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Goodwill And Other Intangible Assets	Note5 Goodwill and Other Intangible Assets The changes in the carrying amount of goodwill for the year ended December31, 2009, were as follows: Balance Goodwill Balance as of Acquired as of January1, During December31, 2009 the Year* 2009 (In thousands) Electric $ $ $ Natural gas distribution 344,952 784 345,736 Construction services 95,619 4,508 100,127 Pipeline and energy services 1,159 6,698 7,857 Natural gas and oil production Construction materials and contracting 174,005 1,738 175,743 Other Total $ 615,735 $ 13,728 $ 629,463 * Includes purchase price adjustments that were not material related to acquisitions in a prior period. The changes in the carrying amount of goodwill for the year ended December31, 2008, were as follows: Balance Goodwill Balance as of Acquired as of January1, During December31, 2008 the Year* 2008 (In thousands) Electric $ $ $ Natural gas distribution 171,129 173,823 344,952 Construction services 91,385 4,234 95,619 Pipeline and energy services 1,159 1,159 Natural gas and oil production Construction materials and contracting 162,025 11,980 174,005 Other Total $ 425,698 $ 190,037 $ 615,735 * Includes purchase price adjustments that were not material related to acquisitions in a prior period. Other amortizable intangible assets at December31 were as follows: 2009 2008 (In thousands) Customer relationships $ 24,942 $ 21,842 Accumulated amortization (9,500 ) (6,985 ) 15,442 14,857 Noncompete agreements 12,377 10,080 Accumulated amortization (6,675 ) (5,126 ) 5,702 4,954 Other 10,859 10,949 Accumulated amortization (3,026 ) (2,368 ) 7,833 8,581 Total $ 28,977 $ 28,392 Amortization expense for intangible assets for the years ended December31, 2009, 2008 and 2007, was $5.0million, $5.1million and $4.4million, respectively. Estimated amortization expense for intangible assets is $4.5million in 2010, $4.0 million in 2011, $3.9million in 2012, $3.4million in 2013, $3.0million in 2014 and $10.2 million thereafter.

NOTE 6: REGULATORY ASSETS AND L

NOTE 6: REGULATORY ASSETS AND LIABILITIES
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Regulatory Assets And Liabilities	Note6 Regulatory Assets and Liabilities The following table summarizes the individual components of unamortized regulatory assets and liabilities as of December31: 2009 2008 (In thousands) Regulatory assets: Pension and postretirement benefits (a) $ 91,078 $ 119,868 Deferred income taxes* 85,712 46,855 Natural gas supply derivatives (a) (b) 27,900 89,813 Costs related to potential generation development (a) 15,499 Long-term debt refinancing costs (a) 12,089 9,991 Taxes recoverable from customers (a) 10,102 4,824 Plant costs (a) 7,775 8,534 Natural gas cost recoverable through rate adjustments (b) 982 51,699 Other (a) (b) 12,242 7,978 Total regulatory assets 263,379 339,562 Regulatory liabilities: Plant removal and decommissioning costs (c) 251,143 94,737 Deferred income taxes* 53,835 65,909 Natural gas costs refundable through rate adjustments (d) 37,356 64 Taxes refundable to customers (c) 34,571 25,642 Natural gas supply derivatives (c) 5,540 Other (c) (d) 17,767 7,460 Total regulatory liabilities 394,672 199,352 Net regulatory position $ (131,293 ) $ 140,210 *Represents deferred income taxes related to regulatory assets and liabilities. (a) Included in deferred charges and other assets on the Consolidated Balance Sheets. (b) Included in prepayments and other current assets on the Consolidated Balance Sheets. (c) Included in other liabilities on the Consolidated Balance Sheets. (d) Included in other accrued liabilities on the Consolidated Balance Sheets. The regulatory assets are expected to be recovered in rates charged to customers. A portion of the Company's regulatory assets are not earning a return; however, these regulatory assets are expected to be recovered from customers in future rates. In 2009, the Company determined that plant removal costs related to recent acquisitions should be reclassified from accumulated depreciation to a regulatory liability. This reclassification is reflected in the preceding table. If, for any reason, the Company's regulated businesses cease to meet the criteria for application of regulatory accounting for all or part of their operations, the regulatory assets and liabilities relating to those portions ceasing to meet such criteria would be removed from the balance sheet and included in the statement of income as an extraordinary itemin the period in which the discontinuance of regulatory accounting occurs.

NOTE 7: DERIVATIVE INSTRUMENTS

NOTE 7: DERIVATIVE INSTRUMENTS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Derivative Instruments	Note7 Derivative Instruments Derivative instruments, including certain derivative instruments embedded in other contracts, are required to be recorded on the balance sheet as either an asset or liability measured at fair value. The Companys policy is to not offset fair value amounts for derivative instruments, and as a result the Companys derivative assets and liabilities are presented gross on the Consolidated Balance Sheets. Changes in the derivative instrument's fair value are recognized currently in earnings unless specific hedge accounting criteria are met. Accounting for qualifying hedges allows derivative gains and losses to offset the related results on the hedged item in the income statement and requires that a company must formally document, designate and assess the effectiveness of transactions that receive hedge accounting treatment. In the event a derivative instrument being accounted for as a cash flow hedge does not qualify for hedge accounting because it is no longer highly effective in offsetting changes in cash flows of a hedged item; if the derivative instrument expires or is sold, terminated or exercised; or if management determines that designation of the derivative instrument as a hedge instrument is no longer appropriate, hedge accounting would be discontinued and the derivative instrument would continue to be carried at fair value with changes in its fair value recognized in earnings. In these circumstances, the net gain or loss at the time of discontinuance of hedge accounting would remain in accumulated other comprehensive income (loss) until the period or periods during which the hedged forecasted transaction affects earnings, at which time the net gain or loss would be reclassified into earnings. In the event a cash flow hedge is discontinued because it is unlikely that a forecasted transaction will occur, the derivative instrument would continue to be carried on the balance sheet at its fair value, and gains and losses that had accumulated in other comprehensive income (loss) would be recognized immediately in earnings. In the event of a sale, termination or extinguishment of a foreign currency derivative, the resulting gain or loss would be recognized immediately in earnings. The Company's policy requires approval to terminate a derivative instrument prior to its original maturity. As of December31, 2009, the Company had no outstanding foreign currency or interest rate hedges. Cascade and Intermountain At December31, 2009, Cascade and Intermountain held natural gas swap agreements, with total forward notional volumes of 12.1million MMBtu, which were not designated as hedges. Cascade and Intermountain utilize natural gas swap agreements to manage a portion of their regulated natural gas supply portfolios in order to manage fluctuations in the price of natural gas related to core customers in accordance with authority granted by the IPUC, WUTC and OPUC. Core customers consist of residential, commercial and smaller industrial customers. The fair value of the derivative instrument must be estimated as of the end of each reporting period and is recorded on the Consolidated Balance Sheets as an asset or a

NOTE 8: FAIR VALUE MEASUREMENTS

NOTE 8: FAIR VALUE MEASUREMENTS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Fair Value Measurements	Note8 Fair Value Measurements On January1, 2008, the Company elected to measure its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. These investments had previously been accounted for as available-for-sale investments. The Company anticipates using these investments to satisfy its obligations under its unfunded, nonqualified benefit plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $34.8million and $27.7million as of December31, 2009 and 2008, respectively, are classified as Investments on the Consolidated Balance Sheets. The increase in the fair value of these investments for the year ended December31, 2009, was $7.1million (before tax). The decrease in the fair value of these investments for the year ended December31, 2008, was $8.6 million (before tax). The change in fair value, which is considered part of the cost of the plan, is classified in operation and maintenance expense on the Consolidated Statements of Income. The Company did not elect the fair value option for its remaining available-for-sale securities, which are auction rate securities. The Companys auction rate securities, which totaled $11.4million at December31, 2009 and 2008, are accounted for as available-for-sale and are recorded at fair value. The fair value of the auction rate securities approximate cost and, as a result, there are no accumulated unrealized gains or losses recorded in accumulated other comprehensive income (loss) on the Consolidated Balance Sheets related to these investments. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The statement establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs. The Companys assets and liabilities measured at fair value on a recurring basis are as follows: Fair Value Measurements at December31, 2009, Using Quoted Prices in Active Markets for Identical Assets (Level1) Significant Other Observable Inputs (Level2) Significant Unobservable Inputs (Level3) Collateral Provided to Counterparties Balance at December31, 2009 (In thousands) Assets: Money market funds $ 9,124 $ 151,000 $ $ $ 160,124 Available-for-sale securities 9,078 37,141 46,219 Commodity derivative instruments - current 7,761 7,761 Commodity derivative instruments - noncurrent 2,734 2,734 Total assets measured at fair value $ 18,202 $ 198,636 $ $ $ 216,838 Liabilities: Commodity derivative instruments - current $ $ 36,907 $ $ $ 36,907 Commodity derivative instruments - noncurrent 4,870 4

NOTE 9: DEBT

NOTE 9: DEBT
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Debt	Note9 Debt Certain debt instruments of the Company and its subsidiaries, including those discussed below, contain restrictive covenants and cross-default provisions. In order to borrow under the respective credit agreements, the Company and its subsidiaries must be in compliance with the applicable covenants and certain other conditions, all of which the Company and its subsidiaries, as applicable, were in compliance with at December 31,2009. In the event the Company and its subsidiaries do not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued. The following table summarizes the outstanding credit facilities of the Company and its subsidiaries: Company Facility Facility Limit Amount Outstanding at December31, 2009 Amount Outstanding at December31, 2008 Letters of Credit at December31, 2009 Expiration Date (Dollars in millions) MDU Resources Group, Inc. Commercial paper/Revolving credit agreement (a) $ 125.0 $ (b) $ 22.5 (b) $ 6/21/11 MDU Energy Capital, LLC Master shelf agreement $ 175.0 $ 165.0 $ 165.0 $ 8/14/10 (c) Cascade Natural Gas Corporation Revolving credit agreement $ 50.0 (d) $ $ 48.1 $ 1.9 (e) 12/28/12 (f) Intermountain Gas Company Revolving credit agreement $ 65.0 (g) $ 10.3 $ 36.5 $ 8/31/10 Centennial Energy Holdings, Inc. Commercial paper/Revolving credit agreement (h) $ 400.0 $ (b) $ 150.0 (b) $ 26.4 (e) 12/13/12 Williston Basin Interstate Pipeline Company Uncommitted long-term private shelf agreement $ 125.0 $ 87.5 $ 72.5 $ 12/23/10 (i) (a) The $125 million commercial paper program is supported by a revolving credit agreement with various banks totaling $125 million (provisions allow for increased borrowings, at the option of the Company on stated conditions, up to a maximum of $150 million). There were no amounts outstanding under the credit agreement. (b) Amount outstanding under commercial paper program. (c) Or such time as the agreement is terminated by either of the parties thereto. (d) Certain provisions allow for increased borrowings, up to a maximum of $75 million. (e) The outstanding letters of credit, as discussed in Note 19, reduce amounts available under the credit agreement. (f) Provisions allow for an extension of up to two years upon consent of the banks. (g) Certain provisions allow for increased borrowings, up to a maximum of $70million. (h) The $400 million commercial paper program is supported by a revolving credit agreement with various banks totaling $400 million (provisions allow for increased borrowings, at the option of Centennial on stated conditions, up to a maximum of $450 million). There were no amounts outstanding under the credit agreement. (i) Certain provisions allow for an extension to December23,2011.

NOTE 10: ASSET RETIREMENT OBLIG

NOTE 10: ASSET RETIREMENT OBLIGATIONS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Asset Retirement Obligations	Note10 Asset Retirement Obligations The Company records obligations related to the plugging and abandonment of natural gas and oil wells, decommissioning of certain electric generating facilities, reclamation of certain aggregate properties, special handling and disposal of hazardous materials at certain electric generating facilities, natural gas distribution and transmission facilities and buildings, and certain other obligations associated with leased properties. A reconciliation of the Company's liability, which is included in other liabilities, for the years ended December31 was as follows: 2009 2008 (In thousands) Balance at beginning of year $ 70,147 $ 64,453 Liabilities incurred 2,418 2,943 Liabilities acquired 2,369 Liabilities settled (9,319 ) (3,188 ) Accretion expense 3,385 3,191 Revisions in estimates 9,548 207 Other 180 172 Balance at end of year $ 76,359 $ 70,147 The Company believes that any expenses related to asset retirement obligations at the Companys regulated operations will be recovered in rates over time and, accordingly, defers such expenses as regulatory assets. The fair value of assets that are legally restricted for purposes of settling asset retirement obligations at December31, 2009 and 2008, was $5.9million.

NOTE 11: PREFERRED STOCKS

NOTE 11: PREFERRED STOCKS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Preferred Stocks	Note11 Preferred Stocks Preferred stocks at December31 were as follows: 2009 2008 (Dollars in thousands) Authorized: Preferred 500,000 shares, cumulative, par value $100, issuable in series Preferred stock A 1,000,000 shares, cumulative, without par value, issuable in series (none outstanding) Preference 500,000 shares, cumulative, without par value, issuable in series (none outstanding) Outstanding: 4.50% Series 100,000 shares $ 10,000 $ 10,000 4.70% Series 50,000 shares 5,000 5,000 Total preferred stocks $ 15,000 $ 15,000 The 4.50% Series and 4.70% Series preferred stocks outstanding are subject to redemption, in whole or in part, at the option of the Company with certain limitations on 30days notice on any quarterly dividend date at a redemption price, plus accrued dividends, of $105per share and $102per share, respectively. In the event of a voluntary or involuntary liquidation, all preferred stock series holders are entitled to $100per share, plus accrued dividends. The affirmative vote of two-thirds of a series of the Company's outstanding preferred stock is necessary for amendments to the Company's charter or bylaws that adversely affect that series; creation of or increase in the amount of authorized stock ranking senior to that series (or an affirmative majority vote where the authorization relates to a new class of stock that ranks on parity with such series); a voluntary liquidation or sale of substantially all of the Company's assets; a merger or consolidation, with certain exceptions; or the partial retirement of that series of preferred stock when all dividends on that series of preferred stock have not been paid. The consent of the holders of a particular series is not required for such corporate actions if the equivalent vote of all outstanding series of preferred stock voting together has consented to the given action and no particular series is affected differently than any other series. Subject to the foregoing, the holders of common stock exclusively possess all voting power. However, if cumulative dividends on preferred stock are in arrears, in whole or in part, for one year, the holders of preferred stock would obtain the right to one vote per share until all dividends in arrears have been paid and current dividends have been declared and set aside.

NOTE 12: COMMON STOCK

NOTE 12: COMMON STOCK
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Common Stock	Note12 Common Stock The Stock Purchase Plan provides interested investors the opportunity to make optional cash investments and to reinvest all or apercentage of their cash dividends in shares of the Company's common stock. The K-Plan is partially funded with the Company's common stock. From January 2007 through March 2007 and October1, 2008 through October21, 2008, the Stock Purchase Plan and K-Plan, with respect to Company stock, were funded with shares of authorized but unissued common stock. From April 2007 through September30, 2008, and October22, 2008 through December2009, purchases of shares of common stock on the open market were used to fund the Stock Purchase Plan and K-Plan. At December31, 2009, there were 23.2 million shares of common stock reserved for original issuance under the Stock Purchase Plan and K-Plan. The Company depends on earnings from its divisions and dividends from its subsidiaries to pay dividends on common stock. The declaration and payment of dividends is at the sole discretion of the board of directors, subject to limitations imposed by state laws, applicable regulatory limitations, and compliance with the requirements of the Companys credit agreements. These requirements are not expected to affect the Companys ability to pay dividends in the near term.

NOTE 13: STOCK BASED COMPENSATI

NOTE 13: STOCK BASED COMPENSATION
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Stock-Based Compensation	Note13 Stock-Based Compensation The Company has several stock-based compensation plans and is authorized to grant options, restricted stock and stock for up to 16.9million shares of common stock and has granted options, restricted stock and stock of 7.3million shares through December31, 2009. The Company generally issues new shares of common stock to satisfy stock option exercises, restricted stock, stock and performance share awards. Total stock-based compensation expense was $3.4million, net of income taxes of $2.2million in 2009; $3.7million, net of income taxes of $2.3million in 2008; and $4.7million, net of income taxes of $3.1million in 2007. As of December31, 2009, total remaining unrecognized compensation expense related to stock-based compensation was approximately $5.6million (before income taxes) which will be amortized over a weighted average period of 1.5 years. Stock options The Company has stock option plans for directors, key employees and employees. The Company has not granted stock options since 2003. Options granted to key employees automatically vest after nine years, but the plan provides for accelerated vesting based on the attainment of certain performance goals or upon a change in control of the Company, and expire 10 years after the date of grant. Options granted to directors and employees vest at the date of grant and three years after the date of grant, respectively, and expire 10years after the date of grant. The fair value of each option outstanding was estimated on the date of grant using the Black-Scholes option-pricing model. A summary of the status of the stock option plans at December31, 2009, and changes during the year then ended was as follows: Number of Shares Weighted Average Exercise Price Balance at beginning of year 1,003,824 $ 13.39 Forfeited (24,188 ) 13.22 Exercised (154,765 ) 13.23 Balance at end of year 824,871 13.42 Exercisable at end of year 799,703 $ 13.41 Summarized information about stock options outstanding and exercisable as of December31, 2009, was as follows: Options Outstanding Options Exercisable Remaining Weighted Aggregate Weighted Aggregate Range of Contractual Average Intrinsic Average Intrinsic Exercisable Number Life Exercise Value Number Exercise Value Prices Outstanding in Years Price (000's) Exercisable Price (000's) $ 9.61 12.00 12,131 .5 $ 9.93 $ 166 12,131 $ 9.93 $ 166 12.01 14.50 745,970 1.2 13.21 7,751 726,235 13.21 7,545 14.51 17.13 66,770 1.2 16.48 475 61,337 16.51 435 Balance at end of year 824,871 1.2 $ 13.42 $ 8,392 799,703 $ 13.41 $ 8,146 The aggregate intrinsic value in the preceding table represents the total intrinsic value (before in

NOTE 14: INCOME TAXES

NOTE 14: INCOME TAXES
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Income Taxes	Note14 Income Taxes The components of income (loss) before income taxes for each of the years ended December31 were as follows: 2009 2008 2007 (In thousands) United States $ (227,021 ) $ 436,029 $ 508,210 Foreign 7,655 5,120 4,600 Income (loss) before income taxes $ (219,366 ) $ 441,149 $ 512,810 Income tax expense (benefit) for the years ended December31 was as follows: 2009 2008 2007 (In thousands) Current: Federal $ 64,389 $ 82,279 $ 106,399 State 8,284 (184 ) 15,135 Foreign 254 (104 ) 235 72,927 81,991 121,769 Deferred: Income taxes Federal (147,607 ) 59,963 58,030 State (22,370 ) 5,332 9,656 Investment tax credit net 213 (405 ) (414 ) (169,764 ) 64,890 67,272 Change in uncertain tax benefits 562 422 869 Change in accrued interest 183 173 114 Total income tax expense (benefit) $ (96,092 ) $ 147,476 $ 190,024 Components of deferred tax assets and deferred tax liabilities recognized at December31 were as follows: 2009 2008 (In thousands) Deferred tax assets: Regulatory matters $ 85,712 $ 46,855 Accrued pension costs 79,052 93,371 Asset retirement obligations 24,091 22,707 Deferred compensation 11,411 12,015 Other 59,763 62,456 Total deferred tax assets 260,029 237,404 Deferred tax liabilities: Depreciation and basis differences on property, plant and equipment 601,426 562,326 Basis differences on natural gas and oil producing properties 116,521 284,231 Regulatory matters 53,835 65,909 Natural gas and oil price swap and collar agreements 30,414 Other 51,070 42,725 Total deferred tax liabilities 822,852 985,605 Net deferred income tax liability $ (562,823 ) $ (748,201 ) As of December31, 2009 and 2008, no valuation allowance has been recorded associated with the above deferred tax assets. The following table reconciles the change in the net deferred income tax liability from December31, 2008, to December31, 2009, to deferred income taxbenefit: 2009 (In thousands) Change in net deferred income tax liability from the preceding table $ (185,378 ) Deferred taxes associated with other comprehensive loss 18,574 Deferred taxes associated with acquisitions 762 Other (3,722 ) Deferred income taxbenefit for the period $ (169,764 ) Total income tax expense (benefit) differs from the amount computed by applying the statutory federal income tax rate to income (loss) before taxes. The reasons for this difference were as follows: Years ended December31, 2009 2008 2007 Amount % Amount % Am

NOTE 15: BUSINESS SEGMENT DATA

NOTE 15: BUSINESS SEGMENT DATA
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Business Segment Data	Note15 Business Segment Data The Companys reportable segments are those that are based on the Companys method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The vast majority of the Companys operations are located within the United States. The Company also has investments in foreign countries, which largely consist of Centennial Resources equity method investment in the Brazilian Transmission Lines. The electric segment generates, transmits and distributes electricity in Montana, North Dakota, South Dakota and Wyoming. The natural gas distribution segment distributes natural gas in those states as well as in Idaho, Minnesota, Oregon and Washington. These operations also supply related value-added products and services. The construction services segment specializes in constructing and maintaining electric and communication lines, gas pipelines, fire suppression systems, and external lighting and traffic signalization equipment. This segment also provides utility excavation services and inside electrical wiring, cabling and mechanical services, sells and distributes electrical materials, and manufactures and distributes specialty equipment. The pipeline and energy services segment provides natural gas transportation, underground storage and gathering services through regulated and nonregulated pipeline systems primarily in the Rocky Mountain and northern Great Plains regions of the United States. This segment also provides cathodic protection and energy-related services. The natural gas and oil production segment is engaged in natural gas and oil acquisition, exploration, development and production activities in the Rocky Mountain and Mid-Continent regions of the United States and in and around the Gulf of Mexico. The construction materials and contracting segment mines aggregates and markets crushed stone, sand, gravel and related construction materials, including ready-mixed concrete, cement, asphalt, liquid asphalt and other value-added products. It also performs integrated contracting services. This segment operates in the central, southern and western United States and Alaska and Hawaii. The Other category includes the activities of Centennial Capital, which insures various types of risks as a captive insurer for certain of the Companys subsidiaries. The function of the captive insurer is to fund the deductible layers of the insured companies general liability and automobile liability coverages. Centennial Capital also owns certain real and personal property. The Other category also includes Centennial Resources' equity method investment in the Brazilian Transmission Lines. The information below follows the same accounting policies as described in the Summary of Significant Accounting Policies. Information on the Company's businesses as of December31 and for the years then ended was as follows: 2009 2008 2007 (In thousands) External operating revenues: Electric $ 196,171 $ 208,326 $ 193,367 Natural gas distribution 1,072,776 1,036,109 532,997

NOTE 16: EMPLOYEE BENEFIT PLANS

NOTE 16: EMPLOYEE BENEFIT PLANS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Employee Benefit Plans	Note16 Employee Benefit Plans The Company has noncontributory defined benefit pension plans and other postretirement benefit plans for certain eligible employees. The Company uses a measurement date of December31 for all of its pension and postretirement benefit plans. Effective January1, 2006, the Company discontinued defined pension plan benefits to all nonunion and certain union employees hired after December31, 2005. These employees that would have been eligible for defined pension plan benefits are eligible to receive additional defined contribution plan benefits. In 2009, the Company evaluated several provisions of its employee defined benefit plans for nonunion and certain union employees. As a result of this evaluation, the Company determined that, effective January 1, 2010, all benefit and service accruals of these plans were frozen. These employees will be eligible to receive additional defined contribution plan benefits. Effective January 1, 2010, eligibility to receive retiree medical benefits was modified at certain of the Companys businesses. Current employees who attain age 55 with 10 years of continuous service by December 31, 2010, will be provided the current retiree medical insurance benefits or can elect the new benefit, if desired, regardless of when they retire. All other current employees must meet the new eligibility criteria of age 60 and 10 years of continuous service at the time they retire. These employees will be eligible for a specified company funded Retiree Reimbursement Account. Employees hired after December 31, 2009, will not be eligible for retiree medical benefits. Changes in benefit obligation and plan assets for the year ended December31, 2009 and 2008, and amounts recognized in the Consolidated Balance Sheets at December31, 2009 and 2008, were as follows: Pension Benefits Other Postretirement Benefits 2009 2008 2009 2008 (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 358,525 $ 359,923 $ 94,325 $ 81,581 Service cost 8,127 8,812 2,206 1,977 Interest cost 21,919 21,264 5,465 5,079 Plan participants' contributions 2,369 2,120 Amendments (9,319 ) (382 ) Actuarial (gain) loss 26,188 (8,336 ) 813 763 Curtailment gain (38,166 ) Acquisition 9,872 Benefits paid (23,678 ) (23,138 ) (7,708 ) (6,685 ) Benefit obligation at end of year 352,915 358,525 88,151 94,325 Change in net plan assets: Fair value of plan assets at beginning of year 226,214 330,966 60,085 73,684 Actual gain (loss) on plan assets 42,084 (83,960 ) 8,600 (20,058 ) Employer contribution 10,707 2,346 3,638 3,212 Plan participants' contributions 2,369 2,120 Acquisition 7,812 Benefits paid (23,678 ) (23,138 ) (7,7

NOTE 17: JOINTLY OWNED FACILITI

NOTE 17: JOINTLY OWNED FACILITIES
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Jointly Owned Facilities	Note17 Jointly Owned Facilities The consolidated financial statements include the Company's 22.7percent and 25.0percent ownership interests in the assets, liabilities and expenses of the Big Stone Station and the Coyote Station, respectively. Each owner of the Big Stone and Coyote stations is responsible for financing its investment in the jointly owned facilities. The Company's share of the Big Stone Station and Coyote Station operating expenses was reflected in the appropriate categories of operating expenses in the Consolidated Statements of Income. At December31, the Company's share of the cost of utility plant in service and related accumulated depreciation for the stations was as follows: 2009 2008 (In thousands) Big Stone Station: Utility plant in service $ 60,220 $ 61,030 Less accumulated depreciation 39,940 39,473 $ 20,280 $ 21,557 Coyote Station: Utility plant in service $ 131,042 $ 127,151 Less accumulated depreciation 82,402 82,018 $ 48,640 $ 45,133 In April 2009, the Company purchased a 25 MW ownership interest in the Wygen III electric generation facility, which is under construction near Gillette, Wyoming, and is expected to be online in the second quarter of 2010. The Companys balance of construction work in progress related to this facility that is included in property, plant and equipment on the Consolidated Balance Sheets at December 31, 2009, is $56.1 million.

NOTE 18: REGULATORY MATTERS AND

NOTE 18: REGULATORY MATTERS AND REVENUES SUBJECT TO REFUND
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Regulatory Matters And Revenues Subject To Refund	Note18 Regulatory Matters and Revenues Subject to Refund In November 2006, Montana-Dakota filed an application with the NDPSC requesting an advance determination of prudence of Montana-Dakota's ownership interest in Big Stone StationII. In August 2008, the NDPSC approved Montana-Dakotas request for advance determination of prudence for ownership in the proposed Big Stone Station II for a minimum of 121.8MW up to a maximum of 133MW and a proportionate ownership share of the associated transmission electric resources. The intervenors in the proceeding appealed the NDPSC order to the North Dakota District Court which affirmed the order of the NDPSC. The intervenors then appealed the North Dakota District Court order to the North Dakota Supreme Court. The Big Stone Station II participants subsequently decided not to proceed with the project and on December2, 2009, Montana-Dakota filed an application with the NDPSC for a determination that Montana-Dakotas continued participation in the Big Stone Station II is no longer prudent. The parties have stipulated that the intervenors will move to dismiss their appeal to the North Dakota Supreme Court if the NDPSC grants Montana-Dakotas pending application for a determination that its participation in the Big Stone Station II is no longer prudent. On December4, 17, and 23, 2009, Montana-Dakota filed an application with the NDPSC, SDPUC, and MTPSC, respectively, for authority to defer the costs incurred for securing new electric generation, primarily Big Stone Station II, until the next general rate case. On August14, 2009, Montana-Dakota filed an application with the WYPSC for an electric rate increase. Montana-Dakota requested a total increase of $6.2million annually or approximately 31percent above current rates. The rate increase request was necessitated by the Companys 25MW ownership interest in the Wygen III power generation facility currently under construction near Gillette, Wyoming. The generation will replace a portion of the purchased power currently used to serve its Wyoming system. On January14, 2010, Montana-Dakota filed a supplement to the application to reflect the inclusion of bonus tax depreciation on the Wygen III plant, reducing its request to a $5.1million annual increase or approximately 25 percent above current rates. A hearing has been set for February23, 2010. In December 1999, Williston Basin filed a general natural gas rate change application with the FERC. Williston Basin began collecting such rates effective June1, 2000, subject to refund. There had been one remaining issue outstanding related to this rate change application regarding certain service restrictions. After various steps in this proceeding, including a Williston Basin Request for Rehearing, an appeal to the D.C. Appeals Court, and a remand to FERC, the FERC, on October30, 2009, issued its Order on Remand in which it upheld its previous decision. No party requested rehearing of the order, which is now final, and no issue is outstanding in this application.

NOTE 19: COMMITMENTS AND CONTIN

NOTE 19: COMMITMENTS AND CONTINGENCIES
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Contingencies	Note19 Commitments and Contingencies Litigation Coalbed Natural Gas Operations Fidelitys CBNG operations are and have been the subject of numerous lawsuits in Montana and Wyoming. The current cases involve the permitting and use of water produced in connection with Fidelitys CBNG development in the Powder River Basin. Some of these cases challenge the issuance of discharge permits by the Montana DEQ and approval of other water management tools by the MBOGC. In April 2006, the Northern Cheyenne Tribe filed a complaint in Montana Twenty-Second Judicial District Court against the Montana DEQ seeking to set aside Fidelitys renewed direct discharge and treatment permits. The Northern Cheyenne Tribe claimed the Montana DEQ violated the Clean Water Act and the Montana Water Quality Act by failing to include in the permits conditions requiring application of the best practicable control technology currently available and by failing to impose a nondegradation policy like the one the BER adopted soon after the permit was issued. In addition, the Northern Cheyenne Tribe claimed that the actions of the Montana DEQ violated the Montana State Constitutions guarantee of a clean and healthful environment, that the Montana DEQs related environmental assessment was invalid, that the Montana DEQ was required, but failed, to prepare an EIS and that the Montana DEQ failed to consider other alternatives to the issuance of the permits. Fidelity, the NPRC, and the TRWUA were granted leave to intervene in this proceeding. On January12, 2009, the Montana Twenty-Second Judicial District Court decided the case in favor of Fidelity and the Montana DEQ in all respects, denying the motions of the Northern Cheyenne Tribe, TRWUA, and NPRC, and granting the cross-motions of the Montana DEQ and Fidelity in their entirety. As a result, Fidelity may continue to utilize its direct discharge and treatment permits. The NPRC, the TRWUA and the Northern Cheyenne Tribe appealed the decision to the Montana Supreme Court on March9, 11, and 13, 2009, respectively. Fidelitys discharge of water pursuant to its two permits is its primary means for managing CBNG-produced water. Fidelity believes that its discharge permits should, assuming normal operating conditions, allow Fidelity to continue its existing CBNG operations through the expiration of the permits in March 2011. If its permits are set aside, Fidelitys CBNG operations in Montana could be significantly and adversely affected. In October 2003, Tongue Yellowstone Irrigation District, NPRC and MEIC filed a lawsuit in Montana First Judicial District Court challenging the MBOGCs ROD adopting the 2003 Final EIS which analyzed CBNG development in the State of Montana. Through the amendment of the plaintiffs pleadings and as a result of discovery, the defendants have now determined that the primary legal issue before the Court is whether the ROD authorizes the wasting of ground water in violation of the Montana State Constitution and the public trust doctrine. Specifically, the plaintiffs contend that various water management tools, including Fidelitys direct discharge permits, allow for the waste of water. Should the Mon

NOTE 20: SUBSEQUENT EVENTS

NOTE 20: SUBSEQUENT EVENTS
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Subsequent Events	Note20 Subsequent Events The Company evaluated for events or transactions between the balance sheet date and February17, 2010, the date of the issuance of the financial statements, that would require recognition or disclosure in the financial statements.

SUPPLEMENTARY FINANCIAL INFORMA

SUPPLEMENTARY FINANCIAL INFORMATION
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Supplementary Financial Information	Supplementary Financial Information Quarterly Data (Unaudited) The following unaudited information shows selected items by quarter for the years 2009 and 2008: First Second Third Fourth Quarter* Quarter Quarter Quarter ** (In thousands, except per share amounts) 2009 Operating revenues $ 1,094,005 $ 958,040 $ 1,107,927 $ 1,016,529 Operating expenses 1,634,924 857,975 947,654 889,045 Operating income (loss) (540,919 ) 100,065 160,273 127,484 Net income (loss) (343,803 ) 55,311 92,584 72,634 Earnings (loss) per common share: Basic (1.87 ) .30 .50 .39 Diluted (1.87 ) .30 .50 .38 Weighted average common shares outstanding: Basic 183,787 183,964 185,160 187,748 Diluted 183,787 184,398 185,425 188,373 2008 Operating revenues $ 1,121,907 $ 1,251,772 $ 1,333,834 $ 1,295,765 Operating expenses 994,335 1,053,281 1,130,537 1,313,088 Operating income (loss) 127,572 198,491 203,297 (17,323 ) Net income (loss) 71,051 115,507 118,382 (11,267 ) Earnings (loss) per common share: Basic .39 .63 .65 (.06 ) Diluted .39 .63 .64 (.06 ) Weighted average common shares outstanding: Basic 182,599 182,972 183,219 183,603 Diluted 183,130 183,727 184,081 183,603 * 2009 reflects a $384.4million after-tax noncash write-down of natural gas and oil properties. ** 2008 reflects an $84.2million after-tax noncash write-down of natural gas and oil properties. Certain Company operations are highly seasonal and revenues from and certain expenses for such operations may fluctuate significantly among quarterly periods. Accordingly, quarterly financial information may not be indicative of results for a full year. Natural Gas and Oil Activities (Unaudited) Fidelity is involved in the acquisition, exploration, development and production of natural gas and oil resources. Fidelity's activities include the acquisition of producing properties with potential development opportunities, exploratory drilling and the operation and development of production properties. Fidelity shares revenues and expenses from the development of specified properties in the Rocky Mountain and Mid-Continent regions of the United States and in and around the Gulf of Mexico in proportion to its ownership interests. Fidelity owns in fee or holds natural gas leases for the properties it operates in Colorado, Montana, North Dakota, Texas, Utah and Wyoming. These rights are in the Bonny Field in eastern Colorado, the Baker Field in southeastern Montana and southwestern North Dakota, the Bowdoin area in north-central Montana, the Powder River Basin of Montana and Wyoming, th

Valuation Schedule

Valuation Schedule
	12 Months Ended Dec. 31, 2009 USD / shares
Notes To Financial Statements [Abstract]
Valuation Schedule	2. Financial Statement Schedules MDU Resources Group, Inc. ScheduleII - Consolidated Valuation and Qualifying Accounts Years Ended December31, 2009, 2008 and 2007 Additions Balance at Charged to Balance Beginning Costs and at End Description of Year Expenses Other* Deductions** of Year (In thousands) Allowance for doubtful accounts: 2009 $13,691 $12,152 $1,412 $10,606 $16,649 2008 14,635 12,191 2,115 15,250 13,691 2007 7,725 8,799 5,533 7,422 14,635 *Allowance for doubtful accounts for companies acquired and recoveries. **Uncollectible accounts written off. All other schedules are omitted because of the absence of the conditions under which they are required, or because the information required is included in the Company's Consolidated Financial Statements and Notes thereto.

Document Information

Document Information
	12 Months Ended Dec. 31, 2009 USD / shares
Document Information [Text Block]
Document Type	10-K
Amendment Flag	false
Document Period End Date	2009-12-31

Entity Information

Entity Information (USD $)
	12 Months Ended Dec. 31, 2009	Feb. 02, 2010	Jun. 30, 2009
Entity [Text Block]
Entity Registrant Name	MDU RESOURCES GROUP INC
Entity Central Index Key	0000067716
Current Fiscal Year End Date	--12-31
Entity Well Known Seasoned Issuer	Yes
Entity Voluntary Filers	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$3,489,895,496
Entity Common Stock Shares Outstanding		187,863,394