Acquisitions and Divestitures - Impact to Historical Consolidated Statements of Operations Table (Details) - USD ($) $ in Thousands	3 Months Ended									9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018		Jun. 30, 2018	[1]	Mar. 31, 2018	[1]	Sep. 30, 2019	Sep. 30, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	$ 666,027			$ 587,900	[1]					$ 2,022,964	$ 1,607,032	[1]
Equity income, net – affiliates	53,893			54,215	[1]					175,483	133,874	[1]
Net income (loss)	125,223	$ 175,058	$ 211,979	198,560	[1]	$ 67,167		$ 181,010		512,260	446,737	[1]
WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	666,027			587,900	[1]					2,022,964	1,607,032	[1]
Equity income, net – affiliates	53,893			54,215	[1]					175,483	133,874	[1]
Net income (loss)	$ 126,912	$ 176,979	$ 214,450	199,519	[1]	$ 68,123		$ 182,870		$ 518,341	450,512	[1]
Anadarko Midstream Assets [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other				89,714							200,064
Equity income, net – affiliates				11,105							31,122
Net income (loss)				43,883							107,009
Anadarko Midstream Assets [Member] | WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other				89,714							200,064
Equity income, net – affiliates				11,105							31,122
Net income (loss)				43,883							107,009
Anadarko Midstream Assets [Member] | Eliminations [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other				(9,576)							(25,515)
Equity income, net – affiliates				0							0
Net income (loss)				0							0
Anadarko Midstream Assets [Member] | Eliminations [Member] | WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other				(9,576)							(25,515)
Equity income, net – affiliates				0							0
Net income (loss)				0							0
Historical financial data [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other				507,762							1,432,483
Equity income, net – affiliates				43,110							102,752
Net income (loss)				154,677							339,728
Historical financial data [Member] | WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other				507,762							1,432,483
Equity income, net – affiliates				43,110							102,752
Net income (loss)				$ 155,636							$ 343,503

[1] Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.