Acquisitions and Divestitures - Impact to Historical Consolidated Statements of Operations Table (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Mar. 31, 2018	[1]	Jun. 30, 2019	Jun. 30, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	$ 685,054		$ 518,078	[1]			$ 1,356,937	$ 1,019,132	[1]
Equity income, net – affiliates	63,598		49,430	[1]			121,590	79,659	[1]
Net income (loss)	175,058	$ 211,979	67,167	[1]	$ 181,010		387,037	248,177	[1]
WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	685,054		518,078	[1]			1,356,937	1,019,132	[1]
Equity income, net – affiliates	63,598		49,430	[1]			121,590	79,659	[1]
Net income (loss)	$ 176,979	$ 214,450	68,123	[1]	$ 182,870		$ 391,429	250,993	[1]
Anadarko Midstream Assets [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			58,686					110,350
Equity income, net – affiliates			10,212					20,017
Net income (loss)			32,604					63,126
Anadarko Midstream Assets [Member] | WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			58,686					110,350
Equity income, net – affiliates			10,212					20,017
Net income (loss)			32,604					63,126
Anadarko Midstream Assets [Member] | Eliminations [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			(8,527)					(15,939)
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			(8,527)					(15,939)
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			467,919					924,721
Equity income, net – affiliates			39,218					59,642
Net income (loss)			34,563					185,051
Historical financial data [Member] | WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			467,919					924,721
Equity income, net – affiliates			39,218					59,642
Net income (loss)			$ 35,519					$ 187,867

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