Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 45
-Paragraph 28
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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
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-Section 35
-Paragraph 32
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- Definition

Fair value portion of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The estimated or actual value of the asset at the end of its useful life or when it is no longer serviceable (cannot be used for its original purpose).

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Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Impairments	$ 148	$ 164,742	$ 178,400
Western Gas Partners, LP [Member] \| Fort Union [Member]
Property, Plant and Equipment [Line Items]
Equity investment impairment loss			3,110
Western Gas Partners, LP [Member] \| Granger Complex [Member]
Property, Plant and Equipment [Line Items]
Impairments			158,800
Western Gas Partners, LP [Member] \| Granger Complex [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 3 Inputs [Member] \| Income Approach Valuation Technique [Member]
Property, Plant and Equipment [Line Items]
Estimated fair value			48,500
Western Gas Partners, LP [Member] \| Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairments			19,600
Western Gas Partners, LP [Member] \| Hilight System [Member]
Property, Plant and Equipment [Line Items]
Impairments			8,200
Western Gas Partners, LP [Member] \| Granger Straddle Plant [Member]
Property, Plant and Equipment [Line Items]
Impairments			3,700
Western Gas Partners, LP [Member] \| Granger Straddle Plant [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 3 Inputs [Member] \| Income Approach Valuation Technique [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value			600
Western Gas Partners, LP [Member] \| Northeast Wyoming Facility [Member]
Property, Plant and Equipment [Line Items]
Impairments			2,000
Western Gas Partners, LP [Member] \| Northeast Wyoming Facility [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 3 Inputs [Member] \| Market Approach Valuation Technique [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value			$ 400