PROPERTY, PLANT AND EQUIPMENT (Tables) (Regulated [Member])

12 Months Ended

Dec. 31, 2014

Regulated [Member]

Property, Plant and Equipment [Line Items]

Property, Plant and Equipment by Property Type

The following table sets forth our property, plant and equipment by property type, for the periods indicated:

	December 31,			December 31,
	2014			2013
	(Thousands of dollars)
Natural gas distribution pipelines and related equipment	$	3,909,881		$	3,703,593
Natural gas transmission pipelines and related equipment	450,810			430,042
General plant and other	418,157			326,004
Construction work in process	71,353			74,435
Property, plant and equipment	4,850,201			4,534,074
Accumulated depreciation and amortization	(1,556,481		)	(1,489,216		)
Net property, plant and equipment	$	3,293,720		$	3,044,858

Average Depreciation Rates for Regulated Property

We compute depreciation expense for distribution operations by applying composite, straight-line rates approved by various regulatory agencies. The average depreciation rates for our property are set forth in the following table for the periods indicated:

Years Ended December 31,
2014	2013	2012
2.0% - 3.0%	2.0% - 3.0%	2.0% - 3.0%