Business segment data

6 Months Ended

Jun. 30, 2012

Segment Reporting [Abstract]

Business segment data

Business segment data

The Company's reportable segments are those that are based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The vast majority of the Company's 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 ECTE.

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 services.

The pipeline and energy services segment provides natural gas transportation, underground storage, processing and gathering services, as well as oil gathering, 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 other energy-related services.

The exploration and production segment is engaged in oil and natural gas 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 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 Other category includes the activities of Centennial Capital, which insures various types of risks as a captive insurer for certain of the Company's 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 ECTE.

The information below follows the same accounting policies as described in Note 1 of the Company's Notes to Consolidated Financial Statements in the 2011 Annual Report. Information on the Company's businesses was as follows:

Three Months Ended June 30, 2012	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	52,955	$	—		$	4,419
Natural gas distribution	116,844		—			(6,411		)
Pipeline and energy services	34,656		8,937			15,851
	204,455		8,937			13,859
Exploration and production	100,232		5,711			17,957
Construction materials and contracting	438,963		3,097			7,791
Construction services	223,858		219			8,684
Other	454		2,028			5,651
	763,507		11,055			40,083
Intersegment eliminations	—		(19,992		)	—
Total	$	967,962	$	—		$	53,942

Three Months Ended June 30, 2011	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	49,986	$	—		$	4,807
Natural gas distribution	164,626		—			1,902
Pipeline and energy services	59,926		12,504			4,772
	274,538		12,504			11,481
Exploration and production	87,390		25,392			21,326
Construction materials and contracting	375,613		—			4,980
Construction services	192,697		5,379			6,138
Other	519		2,301			971
	656,219		33,072			33,415
Intersegment eliminations	—		(45,576		)	—
Total	$	930,757	$	—		$	44,896

Six Months Ended June 30, 2012	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	110,918	$	—		$	11,978
Natural gas distribution	424,733		—			19,097
Pipeline and energy services	63,882		29,347			18,611
	599,533		29,347			49,686
Exploration and production	188,727		17,038			30,887
Construction materials and contracting	588,232		3,248			(17,141		)
Construction services	442,010		244			20,087
Other	2,267		2,355			6,042
	1,221,236		22,885			39,875
Intersegment eliminations	—		(52,232		)	—
Total	$	1,820,769	$	—		$	89,561

Six Months Ended June 30, 2011	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	107,831	$	—		$	13,331
Natural gas distribution	535,010		—			29,418
Pipeline and energy services	109,177		37,245			11,691
	752,018		37,245			54,440
Exploration and production	165,801		50,933			37,596
Construction materials and contracting	519,146		—			(16,423		)
Construction services	394,877		6,596			10,771
Other	720		4,589			1,318
	1,080,544		62,118			33,262
Intersegment eliminations	—		(99,363		)	—
Total	$	1,832,562	$	—		$	87,702

Earnings from electric, natural gas distribution and pipeline and energy services are substantially all from regulated operations. Earnings from exploration and production, construction materials and contracting, construction services and other are all from nonregulated operations.