Property, Plant and Equipment - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Impairments	$ 25,317,000	$ 2,159,000	$ 152,708,000	$ 170,079,000	$ 178,400,000
Western Gas Partners, LP [Member] | Fort Union [Member]
Property, Plant and Equipment [Line Items]
Equity investment impairment loss					3,100,000
Western Gas Partners, LP [Member] | Third Creek Gathering System [Member]
Property, Plant and Equipment [Line Items]
Impairments			125,900,000
Western Gas Partners, LP [Member] | Third Creek Gathering System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value	1,800,000		1,800,000
Western Gas Partners, LP [Member] | Kitty Draw Gathering System [Member]
Property, Plant and Equipment [Line Items]
Impairments			8,100,000
Western Gas Partners, LP [Member] | Kitty Draw Gathering System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value	0		0
Western Gas Partners, LP [Member] | Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairments			18,700,000		19,600,000
Western Gas Partners, LP [Member] | GNB NGL Pipeline [Member]
Property, Plant and Equipment [Line Items]
Impairments			10,900,000
Western Gas Partners, LP [Member] | GNB NGL Pipeline [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Income Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated fair value	10,000,000		10,000,000
Western Gas Partners, LP [Member] | Chipeta Complex [Member]
Property, Plant and Equipment [Line Items]
Impairments			5,600,000
Western Gas Partners, LP [Member] | Chipeta Complex [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value	$ 1,500,000		$ 1,500,000
Western Gas Partners, LP [Member] | Granger Complex [Member]
Property, Plant and Equipment [Line Items]
Impairments					158,800,000
Western Gas Partners, LP [Member] | Granger Complex [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Income Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated fair value					48,500,000
Western Gas Partners, LP [Member] | Hilight System [Member]
Property, Plant and Equipment [Line Items]
Impairments					8,200,000
Western Gas Partners, LP [Member] | Granger Straddle Plant [Member]
Property, Plant and Equipment [Line Items]
Impairments					3,700,000
Western Gas Partners, LP [Member] | Granger Straddle Plant [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Income Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value					600,000
Western Gas Partners, LP [Member] | Northeast Wyoming Facility [Member]
Property, Plant and Equipment [Line Items]
Impairments					2,000,000
Western Gas Partners, LP [Member] | Northeast Wyoming Facility [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value					$ 400,000