2.2.0.25falsefalse1300 - Disclosure - Subsequent Eventstruefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $D2010http://www.sec.gov/CIK0001166036duration2010-01-01T00:00:002010-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDPerShareDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2true0mwe_SubsequentEventsDisclosureAbstractmwefalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseSubsequent Events3false0us-gaap_ScheduleOfSubsequentEventsTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00<table style="font-size:10pt; font-family:'Times New Roman',times,serif;"> <tr> <td> 30. Subsequent Events <ul> <li style="list-style: none"> Langley Acquisition</li></ul>         On January 3, 2011, MarkWest Energy Appalachia, L.L.C. ("MarkWest Appalachia"), a wholly-owned subsidiary of the Partnership, entered into a Purchase and Sale Agreement (the "Agreement") with EQT Gathering, LLC, a subsidiary of EQT Corporation (together with all of its affiliates, "EQT"). Pursuant to the Agreement, MarkWest Appalachia agreed to acquire gas processing facilities located near Langley and Maytown, Kentucky, consisting of a cryogenic natural gas processing plant with a capacity of approximately 100 MMcf/d and a refrigeration processing plant with a capacity of approximately 75 MMcf/d (together, the "Processing Facilities"), a partially constructed natural gas liquids pipeline (the "Ranger Pipeline") extending through parts of Kentucky and West Virginia, and certain other related assets, for a purchase price of approximately $230 million, subject to customary purchase price adjustments. We refer to this acquisition as the Langley Acquisition. In connection with the Langley Acquisition, MarkWest Appalachia will complete the construction of the Ranger Pipeline to connect the Processing Facilities to MarkWest Appalachia's existing natural gas liquids pipeline that transports natural gas liquids to MarkWest Appalachia's Siloam fractionation facility in South Shore, Kentucky. The transaction closed on February 1, 2011. The Partnership has not completed its valuation and purchase price allocation of the acquired assets and liabilities.         Concurrently with the closing of the Langley Acquisition, MarkWest Appalachia and EQT, entered into a long-term gas processing agreement, pursuant to which MarkWest Appalachia will process certain natural gas owned or controlled by EQT at the Processing Facilities. Under the terms of the gas processing agreement, MarkWest Appalachia will also install an additional cryogenic natural gas processing plant with a capacity of at least 60 MMcf/d in 2012. MarkWest Appalachia and EQT also entered into a long-term natural gas liquids exchange and marketing agreement, which replaced an existing transportation, fractionation and marketing agreement between MarkWest Appalachia and EQT. Pursuant to the natural gas liquids exchange and marketing agreement, natural gas liquids extracted from EQT's gas at the Processing Facilities will be exchanged for fractionated natural gas liquid products at MarkWest Appalachia's Siloam fractionation plant, and MarkWest Appalachia will market those fractionated products on behalf of EQT. <ul> <li style="list-style: none"> Embedded derivative extension</li></ul>         The Partnership has a commodity contract with a producer in the Appalachia region that creates a floor on the frac spread for gas purchases of 9,000 Dth/d. The commodity contract is a component of a broader regional arrangement that also includes a keep-whole processing agreement. As of December 31, 2009, the producer had exercised its right to extend this contract and the related processing agreement through the first quarter of 2015. This contract is accounted for as an embedded derivative and is recorded at fair value and the changes in fair value are reflected in earnings. In February 2011, the Partnership executed agreements with the producer to extend the commodity contract and the related processing agreement through 2022. <ul> <li style="list-style: none"> Equity Offering</li></ul>         On January 14, 2011, the Partnership completed a public offering of approximately 3.45 million newly issued common units representing limited partner interests, which includes the full exercise of the underwriters' over-allotment option, at a price of $41.20 per common unit. Net proceeds of approximately $138 million were used to partially fund the Partnership's ongoing capital expenditure program, including a portion of the costs associated with acquisition of assets from EQT as discussed above. <ul> <li style="list-style: none"> Senior Notes Offering and Tender Offers </li></ul>         On February 24, 2011, the Partnership closed a public offering of $300 million in aggregate principal amount of 6.5% senior unsecured notes due 2021 ("2021 Senior Notes"). The 2021 Senior Notes mature on August 15, 2021, and interest is payable semi-annually in arrears on February 15 and August 15, commencing August 15, 2011. The Partnership received net proceeds of approximately $296 million after deducting the underwriting fees and other third-party expenses associated with the offering. The Partnership used the net proceeds from this offering to fund the concurrent repurchase of approximately $272.2 million in aggregate principal amount of the Partnership's 2016 Senior Notes, representing approximately 99% of the outstanding 2016 Senior Notes, pursuant to the Partnership's tender offer for any and all of the outstanding 2016 Senior Notes. The tender offer for the 2016 Senior Notes will expire on March 9, 2011. Assuming no additional 2016 Senior Notes are tendered for repurchase prior to the expiration of the tender offer, the Partnership will record a pre-tax loss on redemption of debt of approximately $21 million in the first quarter of 2011, which will consist of approximately $1 million for the non-cash write off of the unamortized discount and deferred finance costs and approximately $20 million for the payment of the related tender premiums and third-party expenses.         On February 9, 2011, the Partnership commenced a tender offer for up to $125 million aggregate principal amount ("Tender Cap") of its outstanding 2018 Senior Notes. On February 23, 2011, the Tender Cap was increased to $170 million and as of such date, holders of the 2018 Senior Notes had tendered approximately $165.5 million in aggregate principal amount of the outstanding 2018 Senior Notes for repurchase at various bid prices within the acceptable range of $1,090.00 to $1,115.00 per $1,000 principal amount. The tender offer for the 2018 Senior Notes expires on March 9, 2011. Assuming the Partnership completes the repurchase of the $165.5 million in aggregate principal amount of 2018 Senior Notes tendered for repurchase as of February 23, 2011 and no additional 2018 Senior Notes are tendered for repurchase prior to the expiration of the tender offer for the 2018 Senior Notes, the Partnership will record a pre-tax loss on redemption of debt of approximately $22 million in the first quarter of 2011, which will consist of approximately $3 million for the non-cash write off of the unamortized discount and deferred finance costs and approximately $19 million for the payment of the related tender premiums and third-party expenses. </td></tr></table> 30. Subsequent Events Langley Acquisition         On January 3, 2011, MarkWest Energy Appalachia, L.L.C.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes disclosed significant events or transactions that occurred after the balance sheet date, but before the issuance of the financial statements. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, losses resulting from fire or flood, losses on receivables, significant realized and unrealized gains and losses that result from changes in quoted market prices of securities, declines in market prices of inventory, changes in authorized or issued debt (SEC), significant foreign exchange rate changes, substantial loans to insiders or affiliates, significant long-term investments, and substantial dividends not in the ordinary course of business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 11 falsefalseSubsequent Events12Subsequent EventsUnKnownUnKnownUnKnownUnKnownfalsetrue