PROPERTY, PLANT AND EQUIPMENT (Notes)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT

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

	Estimated Useful Lives (Years)	December 31, 2017			December 31, 2016
		(Thousands of dollars)
Nonregulated
Gathering pipelines and related equipment	5 to 40	$	3,613,344		$	3,352,963
Processing and fractionation and related equipment	3 to 40	3,873,709			3,831,966
Storage and related equipment	3 to 54	604,656			558,695
Transmission pipelines and related equipment	5 to 54	700,455			689,804
General plant and other	2 to 60	504,610			487,559
Construction work in process	—	362,253			371,628
Regulated
Storage and related equipment	5 to 25	12,486			13,524
Natural gas transmission pipelines and related equipment	5 to 77	1,406,780			1,345,740
Natural gas liquids transmission pipelines and related equipment	5 to 88	4,340,428			4,309,341
General plant and other	2 to 50	57,902			54,643
Construction work in process	—	83,044			62,634
Property, plant and equipment		15,559,667			15,078,497
Accumulated depreciation and amortization - nonregulated		(1,888,010		)	(1,641,490		)
Accumulated depreciation and amortization - regulated		(973,531		)	(865,604		)
Net property, plant and equipment		$	12,698,126		$	12,571,403

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,
	2017	2016	2015
Natural Gas Liquids	1.9%	1.9%	1.9%
Natural Gas Pipelines	2.1%	2.1%	2.1%

We incurred costs for construction work in process that had not been paid at December 31, 2017, 2016 and 2015, of $92.4 million, $83.0 million and $115.7 million, respectively. Such amounts are not included in capital expenditures (less AFUDC and capitalized interest) on the Consolidated Statements of Cash Flows.

Impairment Charges - The following table sets forth impairment charges on our long-lived assets for the periods indicated:

	Years Ended December 31,
	2017		2016		2015
Natural Gas Gathering and Processing	$	16.0	$	—	$	73.7
Natural Gas Liquids	—		—		10.0
Total Impairment of long-lived assets	$	16.0	$	—	$	83.7

In the third quarter 2017, following a review of nonstrategic assets for potential divestiture, we recorded $16.0 million of noncash impairment charges related to certain nonstrategic gathering and processing assets located in North Dakota.

In 2015, we recorded a $63.5 million noncash impairment charge to long-lived assets in our Natural Gas Gathering and Processing segment related to our wholly owned coal-bed methane natural gas gathering system, which we shut down in 2016. We also recorded noncash impairment charges of $20.2 million for previously idled assets in our Natural Gas Gathering and Processing and Natural Gas Liquids segments, as our expectation for future use of these assets changed.