Commitments and Contingencies - Additional Information (details) - Western Gas Partners [Member] - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Loss Contingencies [Line Items]
Committed capital	$ 24.1
Rent expense associated with office, warehouse and equipment leases	$ 4.2	$ 2.3

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant