2.4.0.81020 - Disclosure - Recent Accounting Pronouncementstruefalsefalse1false falsefalseD2013Q2YTDhttp://www.sec.gov/CIK0001166036duration2013-01-01T00:00:002013-06-30T00:00:001true 1us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Recent Accounting Pronouncements2false 2us-gaap_AccountingChangesAndErrorCorrectionsTextBlockus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00<div style="font-size:10.0pt;font-family:Times New Roman;"> 2. Recent Accounting Pronouncements   In December 2011, the FASB amended the accounting guidance for balance sheet offsetting for financial assets and financial liabilities. The amended guidance is intended to help investors and other financial statement users to better assess the effect or potential effect of offsetting arrangements on a company’s financial position and provides for increased disclosures. The amended guidance is effective for the Partnership retrospectively as of January 1, 2013. Except for additional disclosures included in Note 6 related to our master netting arrangements, the adoption of the amended guidance did not have a material effect on the Partnership’s condensed consolidated financial statements.   </div>falsefalsefalsenonnum:textBlockItemTypenaThe entire disclosure for reporting accounting changes and error corrections. It includes the conveyance of information necessary for a user of the Company's financial information to understand all aspects and required disclosure information concerning all changes and error corrections reported in the Company's financial statements for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22644-107794 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 45 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=6368906&loc=d3e21914-107793 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22595-107794 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22499-107794 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 1.N.Q3) -URI http://asc.fasb.org/extlink&oid=6369664&loc=d3e30840-122693 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 1 -Section N Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 17, 22, 25, 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false0Recent Accounting PronouncementsfalseRecent Accounting PronouncementsUnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.markwest.com/role/DisclosureRecentAccountingPronouncements12