PROPERTY, PLANT AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment by Property Type

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

	Estimated Useful Lives (Years)	December 31, 2018			December 31, 2017
		(Thousands of dollars)
Nonregulated
Gathering pipelines and related equipment	5 to 40	$	3,851,043		$	3,613,344
Processing and fractionation and related equipment	3 to 40	4,171,072			3,873,709
Storage and related equipment	3 to 54	656,455			604,656
Transmission pipelines and related equipment	5 to 54	782,258			700,455
General plant and other	2 to 60	547,424			504,610
Construction work in process	—	797,182			362,253
Regulated
Storage and related equipment	5 to 25	8,987			12,486
Natural gas transmission pipelines and related equipment	5 to 77	1,475,789			1,406,780
Natural gas liquids transmission pipelines and related equipment	5 to 88	4,677,599			4,340,428
General plant and other	2 to 50	61,136			57,902
Construction work in process	—	1,002,018			83,044
Property, plant and equipment		18,030,963			15,559,667
Accumulated depreciation and amortization - nonregulated		(2,168,855		)	(1,888,010		)
Accumulated depreciation and amortization - regulated		(1,095,457		)	(973,531		)
Net property, plant and equipment		$	14,766,651		$	12,698,126

Average Depreciation Rates for Regulated Property

The average depreciation rates for our regulated property are set forth, by segment, in the following table for the periods indicated:

	Years Ended December 31,
	2018	2017	2016
Natural Gas Liquids	1.9%	1.9%	1.9%
Natural Gas Pipelines	2.1%	2.1%	2.1%