Summary of Significant Accounting Policies - Impact of New Accounting Pronouncement - Statements of Operations Table (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Revenues and other		$ 1,990,276	$ 2,248,356	$ 1,804,270
Expenses
Cost of product	[1]	431,921	908,693	494,194
Operation and maintenance	[1]	414,784	315,994	308,010
Depreciation and amortization		337,536	290,874	272,933
Impairments		228,338	178,374	15,535
Income tax expense (benefit)		2,946	4,866	8,372
Net income (loss) attributable to noncontrolling interests		79,083	196,595	251,208
Net income (loss) attributable to Western Gas Equity Partners, LP		369,429	$ 376,607	$ 345,772
Service Revenues - Fee Based [Member]
Revenues
Revenues and other		1,609,245
Service Revenues - Product Based [Member]
Revenues
Revenues and other		85,553
Product Sales [Member]
Revenues
Revenues and other		293,992
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Expenses
Cost of product		1,270,811
Operation and maintenance		414,591
Depreciation and amortization		334,551
Impairments		228,293
Income tax expense (benefit)		2,816
Net income (loss) attributable to noncontrolling interests		86,164
Net income (loss) attributable to Western Gas Equity Partners, LP		343,924
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member] | Service Revenues - Fee Based [Member]
Revenues
Revenues and other		1,499,424
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member] | Service Revenues - Product Based [Member]
Revenues
Revenues and other		0
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member] | Product Sales [Member]
Revenues
Revenues and other		1,306,479
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member]
Expenses
Cost of product		(838,890)
Operation and maintenance		193
Depreciation and amortization		2,985
Impairments		45
Income tax expense (benefit)		130
Net income (loss) attributable to noncontrolling interests		(7,081)
Net income (loss) attributable to Western Gas Equity Partners, LP		25,505
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member] | Service Revenues - Fee Based [Member]
Revenues
Revenues and other		109,821
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member] | Service Revenues - Product Based [Member]
Revenues
Revenues and other		85,553
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member] | Product Sales [Member]
Revenues
Revenues and other		$ (1,012,487)

[1] Cost of product includes product purchases from affiliates (as defined in Note 1) of $193.7 million, $86.0 million and $80.5 million for the years ended December 31, 2018, 2017 and 2016, respectively. Operation and maintenance includes charges from affiliates of $98.8 million, $72.5 million and $72.3 million for the years ended December 31, 2018, 2017 and 2016, respectively. General and administrative includes charges from affiliates of $46.2 million, $39.9 million and $38.9 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 6.