2.2.0.25falsefalse1160 - Disclosure - Asset Retirement Obligationtruefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 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_AssetRetirementObligationDisclosureAbstractmwefalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseAsset Retirement Obligation3false0us-gaap_AssetRetirementObligationDisclosureTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00<table style="font-size:10pt; font-family:'Times New Roman',times,serif;"> <tr> <td> 16. Asset Retirement Obligation         The Partnership's assets subject to asset retirement obligations are primarily certain gas-gathering pipelines and processing facilities, a crude oil pipeline and other related pipeline assets. The Partnership also has land leases that require the Partnership to return the land to its original condition upon termination of the lease. The Partnership reviews current laws and regulations governing obligations for asset retirements and leases, as well as the Partnership's leases and other agreements.         The following is a reconciliation of the changes in the asset retirement obligation from January 1, 2009 to December 31, 2010 (in thousands): <div style="PADDING-RIGHT: 0pt; PADDING-LEFT: 0pt; PADDING-BOTTOM: 0pt; MARGIN-LEFT: 20%; WIDTH: 60%; PADDING-TOP: 0pt; POSITION: relative">   <div align="center"> <table cellspacing="0" cellpadding="0" width="100%" border="0"> <tr style="HEIGHT: 0px"> <td style="FONT-FAMILY: times" align="left" width="10"></td> <td style="FONT-FAMILY: times" align="left"></td> <td style="FONT-FAMILY: times" width="12"></td> <td style="FONT-FAMILY: times" align="right" width="7"></td> <td style="FONT-FAMILY: times" width="88"></td> <td style="FONT-FAMILY: times" width="12"></td> <td style="FONT-FAMILY: times" align="right" width="7"></td> <td style="FONT-FAMILY: times" width="88"></td> <td style="FONT-FAMILY: times" width="12"></td></tr> <tr style="HEIGHT: 0px" valign="bottom"> <th style="FONT-FAMILY: times" align="left" colspan="2">  </th> <th style="FONT-FAMILY: times"> </th> <th style="BORDER-BOTTOM: #000000 1pt solid; FONT-FAMILY: times" align="center" colspan="2">December 31, 2010 </th> <th style="FONT-FAMILY: times"> </th> <th style="BORDER-BOTTOM: #000000 1pt solid; FONT-FAMILY: times" align="center" colspan="2">December 31, 2009 </th> <th style="FONT-FAMILY: times"> </th></tr> <tr style="HEIGHT: 0px" valign="top" bgcolor="#CCEEFF"> <td style="FONT-FAMILY: times" valign="bottom" colspan="2"> Beginning asset retirement obligation</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">$</td> <td style="FONT-FAMILY: times" valign="bottom" align="right">2,877</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">$</td> <td style="FONT-FAMILY: times" valign="bottom" align="right">1,773</td> <td style="FONT-FAMILY: times" valign="bottom"> </td></tr> <tr style="HEIGHT: 0px" valign="top" bgcolor="white"> <td style="FONT-FAMILY: times"> </td> <td style="FONT-FAMILY: times" valign="bottom"> Liabilities incurred</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">915</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">906</td> <td style="FONT-FAMILY: times" valign="bottom"> </td></tr> <tr style="HEIGHT: 0px" valign="top" bgcolor="#CCEEFF"> <td style="FONT-FAMILY: times"> </td> <td style="FONT-FAMILY: times" valign="bottom"> Accretion expense</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">237</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">198</td> <td style="FONT-FAMILY: times" valign="bottom"> </td></tr> <tr style="FONT-SIZE: 1.5pt; HEIGHT: 0px" valign="top"> <td style="FONT-FAMILY: times" valign="bottom" colspan="2"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="BORDER-BOTTOM: #000000 1pt solid; FONT-FAMILY: times" valign="bottom" align="right" colspan="2"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="BORDER-BOTTOM: #000000 1pt solid; FONT-FAMILY: times" valign="bottom" align="right" colspan="2"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td></tr> <tr style="HEIGHT: 0px" valign="top" bgcolor="white"> <td style="FONT-FAMILY: times" valign="bottom" colspan="2"> Ending asset retirement obligation</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">$</td> <td style="FONT-FAMILY: times" valign="bottom" align="right">4,029</td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="FONT-FAMILY: times" valign="bottom" align="right">$</td> <td style="FONT-FAMILY: times" valign="bottom" align="right">2,877</td> <td style="FONT-FAMILY: times" valign="bottom"> </td></tr> <tr style="FONT-SIZE: 1.5pt; HEIGHT: 0px" valign="top"> <td style="FONT-FAMILY: times" valign="bottom" colspan="2"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="BORDER-BOTTOM: #000000 2.25pt double; FONT-FAMILY: times" valign="bottom" align="right" colspan="2"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td> <td style="BORDER-BOTTOM: #000000 2.25pt double; FONT-FAMILY: times" valign="bottom" align="right" colspan="2"> </td> <td style="FONT-FAMILY: times" valign="bottom"> </td></tr></table></div> </div>         At December 31, 2010, 2009, and 2008, there were no assets legally restricted for purposes of settling asset retirement obligations. The asset retirement obligation has been recorded as part of Other long-term liabilities in the accompanying Consolidated Balance Sheets.         In addition to recorded asset retirement obligations, the Partnership has other asset retirement obligations related to certain gathering, processing and other assets as a result of environmental and other legal requirements. The Partnership is not required to perform such work until it permanently ceases operations of the respective assets. Because the Partnership considers the operational life of these assets to be indeterminable, an associated asset retirement obligation cannot be calculated and is not recorded. </td></tr></table> 16. Asset Retirement Obligation         The Partnership's assets subject to asset retirement obligations are primarilyfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescription of the asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. This element may be used for all the disclosures related to asset retirement obligations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 22 falsefalseAsset Retirement Obligation12Asset Retirement ObligationUnKnownUnKnownUnKnownUnKnownfalsetrue