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Commitments and Contingencies - Additional Information (Details) - Western Gas Partners, LP [Member] - USD ($) $ in Millions		12 Months Ended
	Mar. 17, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Liability for remediation and reclamation obligations		$ 1.8	$ 2.2
Rent expense associated with office, warehouse and equipment leases		42.5	$ 35.9	$ 34.1
DBJV Arbitration [Member] \| Pending Litigation [Member]
Loss Contingencies [Line Items]
Gathering Fees Sought In Arbitration		190.0
Fees Sought In Counterclaim		$ 18.0
Percentage recovery from a third party		50.00%
Percentage due to third party		50.00%
Delaware Basin JV Gathering LLC [Member] \| DBJV Arbitration [Member]
Loss Contingencies [Line Items]
Percentage ownership interest	50.00%
Percentage third-party ownership interest	50.00%