Income Taxes - Tax Rate Reconciliation Table (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Income (loss) before income taxes		$ 578,068	$ 605,352	$ 56,630
Statutory tax rate		0.00%	0.00%	0.00%
Adjustments resulting from:
Federal taxes on income		$ 0	$ 0	$ 0
State taxes on income (net of federal benefit) and Texas margin tax expense (benefit)	[1]	4,866	2,093	2,411
Income tax expense (benefit)		$ 4,866	$ 8,372	$ 45,532
Effective tax rate		1.00%	1.00%	80.00%
Change in deferred state income taxes				$ 2,200
Change in Texas margin tax rates				0.25%
Western Gas Partners, LP [Member]
Adjustments resulting from:
Federal taxes on income		$ 0	$ 6,162	$ 42,823
State taxes on income (net of federal benefit) and Texas margin tax expense (benefit)		$ 0	$ 117	$ 298

[1] Includes a reduction of $2.2 million in deferred state income taxes for the year ended December 31, 2015. Texas House Bill 32, signed into law in June 2015, reduced the Texas margin tax rates by 0.25%. The law became effective January 1, 2016. WGP is required to include the impact of the law change on its deferred state income taxes in the period enacted.