Debt and Interest Expense - Interest Expense Table (details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Debt Instrument [Line Items]
Interest expense	$ 13,018,000	[1]	$ 10,977,000	[1],[2]	$ 37,483,000	[1]	$ 30,118,000	[1],[2]
Senior Notes 5 Point 375 Percent Due 2021 [Member] | Senior Notes 4 Percent Due 2022 [Member] | Western Gas Partners [Member]
Table Text Block Supplement [Abstract]
Amortization related to senior notes			400,000				800,000
Third Parties [Member]
Debt Instrument [Line Items]
Interest expense	13,018,000		10,896,000		37,483,000		27,434,000
Third Parties [Member] | Western Gas Partners [Member]
Debt Instrument [Line Items]
Interest expense on long-term debt	14,994,000		11,919,000		43,783,000		28,036,000
Amortization of debt issuance costs and commitment fees	1,135,000	[3]	1,201,000	[3]	3,252,000	[3]	3,225,000	[3]
Capitalized interest	(3,111,000)		(2,224,000)		(9,552,000)		(3,827,000)
Affiliated Entity [Member]
Debt Instrument [Line Items]
Interest expense	0	[4]	81,000	[4]	0	[4]	2,684,000	[4]
Affiliated Entity [Member] | Western Gas Partners [Member]
Debt Instrument [Line Items]
Interest expense on note payable to Anadarko	0	[5]	0	[5]	0	[5]	2,440,000	[5]
Interest expense on affiliate balances	0	[6]	81,000	[6]	0	[6]	244,000	[6]
Senior Notes 2 Point 6 Percent Due 2018 [Member] | Senior Notes 5 Point 375 Percent Due 2021 [Member] | Senior Notes 4 Percent Due 2022 [Member] | Western Gas Partners [Member]
Table Text Block Supplement [Abstract]
Amortization related to senior notes	$ 300,000				$ 800,000

[1] Includes affiliate (as defined in Note 1) interest expense of zero for the three and nine months ended September 30, 2013, and $0.1 million and $2.7 million for the three and nine months ended September 30, 2012, respectively. See Note 8.

[2] Financial information has been recast to include the financial position and results attributable to the Non-Operated Marcellus Interest. See Note 2.

[3] For the three and nine months ended September 30, 2013, includes $0.3 million and $0.8 million, respectively, of amortization of (i) the original issue discount for the June 2012 offering of the 2022 Notes, partially offset by the original issue premium for the October 2012 offering of the 2022 Notes, (ii) original issue discount for the 2021 Notes and 2018 Notes and (iii) underwriters’ fees. For the three and nine months ended September 30, 2012, includes $0.4 million and $0.8 million, respectively, of amortization of the original issue discount and underwriters’ fees for the 2022 Notes issued in June 2012 and the 2021 Notes.

[4] For the three and nine months ended September 30, 2012, includes interest expense recognized on the WES note payable to Anadarko (see Note 8) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada and Lancaster plants. WES repaid the WES note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko related to the construction of the Brasada and Lancaster plants in the fourth quarter of 2012. See Note receivable from and amounts payable to Anadarko within this Note 5.

[5] In June 2012, the WES note payable to Anadarko was repaid in full. See WES note payable to Anadarko within this Note 8.

[6] Imputed interest expense on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada and Lancaster plants. In the fourth quarter of 2012, WES repaid the reimbursement payable to Anadarko associated with the construction of the Brasada and Lancaster plants.