Debt and Interest Expense - Western Gas Partners, LP (Detail) (USD $) Share data in Millions	9 Months Ended		1 Months Ended		3 Months Ended	1 Months Ended		1 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Western Gas Partners Limited Partnership [Member]	Mar. 31, 2011 Western Gas Partners Limited Partnership [Member]	Mar. 31, 2011 Western Gas Partners Limited Partnership [Member] Four Hundred Fifty Million Dollar Revolving Credit Facility [Member]	Mar. 31, 2011 Western Gas Partners Limited Partnership [Member] Eight Hundred Million Dollar Revolving Credit Facility [Member]	Sep. 30, 2011 Western Gas Partners Limited Partnership [Member] Eight Hundred Million Dollar Revolving Credit Facility [Member]	Mar. 31, 2011 Western Gas Partners Limited Partnership [Member] Eight Hundred Million Dollar Revolving Credit Facility [Member] Repayment of Term Loan [Member]
Line of Credit Facility [Line Items]
Line of credit, additional borrowings					$ 310,000,000			$ 250,000,000
Line of credit facility, period						5 years
Line of credit, maximum borrowing capacity					450,000,000		800,000,000
Line of credit facility, repayment					139,000,000
Common units issued to the public			6	4
Proceeds raised from offering by subsidiary	328,000,000	97,000,000	198,000,000	130,000,000
Line of credit, outstanding borrowings							0
Line of credit, remaining borrowing capacity							$ 800,000,000