Description of Business and Basis of Presentation - Impact of New Accounting Pronouncement - Statements of Operations Table (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenues
Revenues and other		$ 507,762	$ 574,695	$ 1,432,483	$ 1,616,338
Expenses
Cost of product	[1]	105,966	239,223	303,518	631,859
Operation and maintenance	[1]	111,359	79,536	300,266	229,444
Depreciation and amortization		82,553	72,539	238,187	216,272
Impairments		25,317	2,159	152,708	170,079	$ 178,400
Income tax (benefit) expense		1,517	510	3,301	4,905
Net income (loss) attributable to noncontrolling interests		47,203	50,399	63,669	146,529
Net income (loss) attributable to Western Gas Equity Partners, LP		107,474	$ 96,202	276,059	$ 277,086
Service Revenues - Fee Based [Member]
Revenues
Revenues and other		409,106		1,146,099
Service Revenues - Product Based [Member]
Revenues
Revenues and other		22,735		67,433
Product Sales [Member]
Revenues
Revenues and other		75,150		217,738
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Expenses
Cost of product		353,641		940,936
Operation and maintenance		111,327		300,098
Depreciation and amortization		81,824		236,102
Impairments				152,663
Income tax (benefit) expense		1,580		3,361
Net income (loss) attributable to noncontrolling interests		40,471		89,339
Net income (loss) attributable to Western Gas Equity Partners, LP		123,002		258,774
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member] | Service Revenues - Fee Based [Member]
Revenues
Revenues and other		396,161		1,096,708
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member] | Service Revenues - Product Based [Member]
Revenues
Revenues and other		0		0
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member] | Product Sales [Member]
Revenues
Revenues and other		366,603		978,127
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member]
Expenses
Cost of product		(247,675)		(637,418)
Operation and maintenance		32		168
Depreciation and amortization		729		2,085
Impairments				45
Income tax (benefit) expense		(63)		(60)
Net income (loss) attributable to noncontrolling interests		6,732		(25,670)
Net income (loss) attributable to Western Gas Equity Partners, LP		(15,528)		17,285
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member] | Service Revenues - Fee Based [Member]
Revenues
Revenues and other		12,945		49,391
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member] | Service Revenues - Product Based [Member]
Revenues
Revenues and other		22,735		67,433
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member] | Product Sales [Member]
Revenues
Revenues and other		$ (291,453)		$ (760,389)

[1] Cost of product includes product purchases from affiliates (as defined in Note 1) of $47.0 million and $131.4 million for the three and nine months ended September 30, 2018, respectively, and $22.9 million and $60.5 million for the three and nine months ended September 30, 2017, respectively. Operation and maintenance includes charges from affiliates of $25.1 million and $68.8 million for the three and nine months ended September 30, 2018, respectively, and $18.1 million and $53.7 million for the three and nine months ended September 30, 2017, respectively. General and administrative includes charges from affiliates of $11.8 million and $35.0 million for the three and nine months ended September 30, 2018, respectively, and $10.4 million and $29.6 million for the three and nine months ended September 30, 2017, respectively. See Note 6.