Equity Investments - Additional Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Equity investment impairment loss	[1]	$ 3,110
Western Gas Partners, LP [Member] | Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment difference between carrying and underlying value		$ (3,100)
Equity investment ownership percentage		14.81%
Equity investment impairment loss		$ 3,110	[1],[2]	$ 3,000	$ 9,500
Western Gas Partners, LP [Member] | Fort Union [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Income Approach Valuation Technique [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment fair value		8,500
Western Gas Partners, LP [Member] | Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment difference between carrying and underlying value		$ 36,200
Equity investment ownership percentage		22.00%
Equity investment impairment loss	[1],[3]	$ 0
Western Gas Partners, LP [Member] | White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment difference between carrying and underlying value		$ (6,900)
Equity investment ownership percentage		10.00%
Equity investment impairment loss	[1],[4]	$ 0
Western Gas Partners, LP [Member] | White Cliffs [Member] | Affiliates [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment ownership percentage		0.40%

[1] Recorded in Impairments in the consolidated statements of operations.

[2] WES has a 14.81% interest in Fort Union, a joint venture that owns a gathering pipeline and treating facilities in the Powder River Basin. Anadarko is the construction manager and physical operator of the Fort Union facilities. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the owners’ firm gathering agreements, require 65% or unanimous approval of the owners.

[3] WES has a 22% interest in Rendezvous, a limited liability company that operates gas gathering facilities in Southwestern Wyoming. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the members’ gas servicing agreements, require unanimous approval of the members.

[4] WES has a 10% interest in White Cliffs, a limited liability company that owns a crude oil pipeline that originates in Platteville, Colorado and terminates in Cushing, Oklahoma. The third-party majority owner is the manager of the White Cliffs operations. Certain business decisions, including, but not limited to, approval of annual budgets and decisions with respect to significant expenditures, contractual commitments, acquisitions, material financings, dispositions of assets or admitting new members, require more than 75% approval of the members.