Equity and Partners' Capital - Additional Information (Details) $ in Millions				1 Months Ended		9 Months Ended	12 Months Ended
	Jun. 07, 2018 shares	May 02, 2017 shares	Mar. 01, 2017 shares	Jun. 30, 2015 $ / unit shares	Nov. 30, 2014 shares	Sep. 30, 2018 shares	Dec. 31, 2016 shares	Dec. 31, 2017 shares	Jul. 31, 2017 USD ($)
Schedule of Investments [Line Items]
Limited partner units owned						218,937,797		218,933,141
7.50% Tangible Equity Units [Member] | Anadarko [Member]
Schedule of Investments [Line Items]
Tangible equity units, number issued				9,200,000
Tangible equity units, rate				7.50%
Tangible equity units, stated amount per unit | $ / unit				50.00
Debt instrument, maturity date				Jun. 07, 2018
Tangible equity units, number settled	9,200,000
7.50% Tangible Equity Units [Member] | Anadarko [Member] | Over-Allotment Option [Member]
Schedule of Investments [Line Items]
Tangible equity units, number issued				1,200,000
7.50% Tangible Equity Units [Member] | Common Units [Member] | Anadarko [Member]
Schedule of Investments [Line Items]
Units issued	8,207,204
Western Gas Equity Partners, LP [Member] | Public [Member]
Schedule of Investments [Line Items]
Limited partner units owned						48,557,636
Ownership interest						22.20%
Western Gas Partners, LP [Member] | Public [Member] | Common Units [Member]
Schedule of Investments [Line Items]
Limited partner units owned						100,465,859
Ownership interest						59.40%
Anadarko [Member] | Western Gas Equity Partners, LP [Member]
Schedule of Investments [Line Items]
Limited partner units owned						170,380,161
Ownership interest						77.80%
Western Gas Equity Partners, LP [Member] | Western Gas Partners, LP [Member]
Schedule of Investments [Line Items]
General partner units owned						2,583,068
General partner's interest						1.50%
Western Gas Equity Partners, LP [Member] | Western Gas Partners, LP [Member] | Common Units [Member]
Schedule of Investments [Line Items]
Limited partner units owned						50,132,046
Ownership interest						29.60%
Western Gas Equity Partners, LP [Member] | Western Gas Partners, LP [Member] | Incentive Distribution Rights [Member]
Schedule of Investments [Line Items]
General partner's interest						100.00%
Western Gas Partners, LP [Member]
Schedule of Investments [Line Items]
Units issued						801,546
Western Gas Partners, LP [Member] | July 2017 COP [Member]
Schedule of Investments [Line Items]
Maximum aggregate principal of common units | $									$ 500.0
Western Gas Partners, LP [Member] | Class C Units [Member]
Schedule of Investments [Line Items]
Units issued						801,546
Class C units, common units issued upon conversion						1
Western Gas Partners, LP [Member] | Class C Units [Member] | Other Subsidiaries of Anadarko [Member]
Schedule of Investments [Line Items]
Units issued					10,913,853
Western Gas Partners, LP [Member] | Series A Preferred Units [Member] | Series A Preferred Units March 2017 Conversion [Member]
Schedule of Investments [Line Items]
Series A Preferred units, percentage converted			50.00%
Series A Preferred units, common units issued upon conversion			1
Western Gas Partners, LP [Member] | Series A Preferred Units [Member] | Series A Preferred Units May 2017 Conversion [Member]
Schedule of Investments [Line Items]
Series A Preferred units, percentage converted		50.00%
Series A Preferred units, common units issued upon conversion		1
Western Gas Partners, LP [Member] | Series A Preferred Units [Member] | Private Investor [Member]
Schedule of Investments [Line Items]
Units issued							21,922,831
Other Subsidiaries of Anadarko [Member] | Western Gas Partners, LP [Member] | Common Units [Member]
Schedule of Investments [Line Items]
Limited partner units owned						2,011,380
Other Subsidiaries of Anadarko [Member] | Western Gas Partners, LP [Member] | Class C Units [Member]
Schedule of Investments [Line Items]
Limited partner units owned						14,045,429
Other Subsidiaries of Anadarko [Member] | Western Gas Partners, LP [Member] | Common and Class C Units [Member]
Schedule of Investments [Line Items]
Ownership interest						9.50%