Condensed Consolidated Balance Sheets (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents ($22,863 and $2,913, respectively)	$ 95,035	$ 67,450
Receivables, net ($12,639 and $43,783, respectively)	188,706	179,209
Inventories ($12,511 and $8,431, respectively)	31,396	23,432
Fair value of derivative instruments	2,835	4,345
Deferred income taxes	16,090	16,090
Other current assets ($746 and $272, respectively)	7,494	8,020
Total current assets	341,556	298,546
Property, plant and equipment ($1,011,845 and $849,986, respectively)	2,967,240	2,613,027
Less: accumulated depreciation ($56,369 and $38,169, respectively)	(363,398)	(294,003)
Total property, plant and equipment, net	2,603,842	2,319,024
Other long-term assets:
Restricted cash ($28,100 and $28,001, respectively)	28,100	28,001
Investment in unconsolidated affiliate	27,633	28,688
Intangibles, net of accumulated amortization of $146,198 and $124,568, respectively	625,737	613,578
Goodwill	67,918	9,421
Deferred financing costs, net of accumulated amortization of $12,839 and $11,445, respectively	33,975	32,901
Deferred contract cost, net of accumulated amortization of $2,106 and $1,950, respectively	1,144	1,300
Fair value of derivative instruments	3,349	417
Other long-term assets ($370 and $383, respectively)	1,771	1,486
Total assets	3,735,025	3,333,362
Current liabilities:
Accounts payable ($14,567 and $5,945, respectively)	152,623	122,473
Accrued liabilities ($49,078 and $64,713, respectively)	135,763	153,869
Deferred income taxes	11	11
Fair value of derivative instruments	78,345	65,489
Total current liabilities	366,742	341,842
Deferred income taxes	6,860	10,427
Fair value of derivative instruments	81,121	66,290
Long-term debt, net of discounts of $1,550 and $1,566, respectively	1,582,102	1,273,434
Other long-term liabilities ($161 and $154, respectively)	115,798	105,349
Commitments and contingencies (Note 11)
Equity:
MarkWest Energy Partners, L.P. partners' capital (75,160 and 71,440 common units issued and outstanding, respectively)	1,106,950	1,070,503
Non-controlling interest in consolidated subsidiaries	475,452	465,517
Total equity	1,582,402	1,536,020
Total liabilities and equity	$ 3,735,025	$ 3,333,362