Debt and Interest Expense - Interest Expense Table (details) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Debt Instrument Line Items
Interest Expense	$ 11,811,000	[1]	$ 9,581,000	[1],[2]
Chipeta Processing Limited Liability Company [Member] | Western Gas Partners [Member]
Debt Instrument Line Items
Capitalized interest			(600,000)
Brasada And Lancaster Agreement [Member] | Western Gas Partners [Member]
Debt Instrument Line Items
Capitalized interest	(3,000,000)		(100,000)
Senior Notes 5 Point 375 Percent Due 2021 [Member] | Western Gas Partners [Member]
Table Text Block Supplement Abstract
Amortization related to Senior Notes			200,000
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
Third Parties [Member]
Debt Instrument Line Items
Interest Expense	11,811,000		8,266,000
Third Parties [Member] | Western Gas Partners [Member]
Debt Instrument Line Items
Interest expense on long-term debt	13,939,000		7,915,000
Amortization of debt issuance costs and commitment fees Credit facility commitment fees	1,053,000	[3]	1,008,000	[3]
Capitalized interest	(3,181,000)	[4]	(657,000)	[4]
Affiliated Entity Member
Debt Instrument Line Items
Interest Expense			1,315,000	[5]
Affiliated Entity Member | Western Gas Partners [Member]
Debt Instrument Line Items
Interest expense on note payable to Anadarko			1,234,000	[6]
Interest expense, net on affiliate balances			$ 81,000	[7]

[1] Includes affiliate (as defined in Note 1) interest expense of zero and $1.3 million for the three months ended March 31, 2013 and 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 months ended March 31, 2013, includes $0.3 million of amortization of (i) the original issue discount for the June 2012 offering 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 (iii) underwriters’ fees. For the three months ended March 31, 2012, includes $0.2 million of amortization of the original issue discount and underwriters’ fees for the 2021 Notes.

[4] For the three months ended March 31, 2013 and 2012, includes zero and $0.6 million, respectively, of capitalized interest associated with capital projects at Chipeta and $3.0 million and $0.1 million, respectively, of capitalized interest associated with the construction of the Brasada and Lancaster gas processing facilities. See Note 5.

[5] Represents interest expense recognized on the note payable to Anadarko (see Note 8) and, for the three months ended March 31, 2012, 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. In the fourth quarter of 2012, WES repaid the note payable to Anadarko and the reimbursement payable to Anadarko related to the construction of the Brasada and Lancaster plants. See Note receivable from and amounts payable to Anadarko within this Note 5.

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

[7] 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, the reimbursement payable to Anadarko related to the construction of the Brasada and Lancaster plants was repaid. See Note 5.