Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 29, 2015
Entity Registrant Name	MARKWEST ENERGY PARTNERS L P
Entity Central Index Key	0001166036
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q2
Common Units
Entity Common Stock, Shares Outstanding		191,379,512
Class B Units
Entity Common Stock, Shares Outstanding		7,981,756