Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Major classifications of property, plant and equipment

The following table presents the major classifications of our property, plant and equipment (in thousands):



	Estimated Useful Life	December 31,
	Estimated Useful Life	2014			2013
	(years)	(in thousands)
Land, land rights and easements	54 – 96	$	130,816		$	128,123
Building and improvements	27 – 64	168,041			163,852
Transmission, distribution, and storage	15 – 85	2,579,861			2,448,821
Generation	25 – 50	1,044,764			533,450
Plant acquisition adjustment	34 – 50	654,835			204,754
Other	2 – 45	326,211			308,345
Construction work in process	–—	221,868			104,891
		5,126,396			3,892,236
Less accumulated depreciation		(1,368,388		)	(1,202,108		)
		$	3,758,008		$	2,690,128

Schedule of jointly owned utility plants

Information relating to our ownership interest in these facilities is as follows (in thousands):



	Big Stone (SD)			Neal #4 (IA)			Coyote (ND)			Colstrip Unit 4 (MT)
December 31, 2014
Ownership percentages	23.4		%	8.7		%	10.0		%	30.0		%
Plant in service	$	61,628		$	59,579		$	46,045		$	292,806
Accumulated depreciation	46,741			27,742			36,649			72,976
December 31, 2013
Ownership percentages	23.4		%	8.7		%	10.0		%	30.0		%
Plant in service	$	61,186		$	57,633		$	46,003		$	290,163
Accumulated depreciation	45,792			29,841			36,076			70,072

- Definition

Tabular disclosure of proportionate interests in jointly owned utility plants. Includes the amount of plants in service, the accumulated provision for depreciation (if available), the amount of plants under construction, and the proportionate share. The amounts presented may be further subdivided to show amounts applicable to plant subcategories (for example, production, transmission, distribution). Includes statements that the amounts represent the utility's share in each joint plant and that it must provide its own financing. Information concerning two or more generating plants on the same site may be combined. States that the utility's share of direct expenses of the joint plants is included in the corresponding operating expenses on its income statement (for example, fuel, maintenance of plant, other operating expense). If the share of direct expenses is charged to purchased power, then disclose the amount so charged and the proportionate amounts charged to specific operating expenses on the records maintained for the joint plants.

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