2.4.0.8000001 - Document - Document and Entity Informationtruefalsefalse1false falsefalsedefaulthttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:001true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:2false 2dei_DocumentTypedei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00485BPOSfalsefalsefalsedei:submissionTypeItemTypestringThe type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word "Other".No definition available.false0Document Type3false 2dei_DocumentPeriodEndDatedei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse002013-02-28falsefalsetruexbrli:dateItemTypedateThe end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.No definition available.false0Document Period End Date4false 2dei_EntityRegistrantNamedei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFS SERIES TRUST XIIIfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringThe exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation 12B -Number 240 -Section 12b -Subsection 1 false0Registrant Name5false 2dei_EntityCentralIndexKeydei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse000000356349falsefalsefalsedei:centralIndexKeyItemTypenaA unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation 12B -Number 240 -Section 12b -Subsection 1 false0Central Index Key6false 2dei_AmendmentFlagdei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsexbrli:booleanItemTypenaIf the value is true, then the document is an amendment to previously-filed/accepted document.No definition available.false0Amendment Flag7false 2dei_DocumentCreationDatedei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse002013-06-27falsefalsetruexbrli:dateItemTypedateThe date the document was made available and submitted, in CCYY-MM-DD format. The date of submission, date of acceptance by the recipient, and the document effective date are all potentially different.No definition available.false0Document Creation Date8false 2dei_DocumentEffectiveDatedei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse002013-06-28falsefalsetruexbrli:dateItemTypedateThe date when a document, upon receipt and acceptance, becomes officially effective, in CCYY-MM-DD format. Usually it is a system-assigned date time value, but it may be declared by the submitter in some cases.No definition available.false0Document Effective Date9false 2rr_ProspectusDaterr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse002013-06-28falsefalsetruexbrli:dateItemTypedateThe date of the prospectus.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 1 -Subsection a -Paragraph 3 false0Prospectus Date10false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2false truefalseS000012219Member_C000033358Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseArr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000033358Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | A11true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:12false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFAXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol13false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse3false truefalseS000012219Member_C000033359Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseCrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000033359Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | C14true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:15false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFCXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol16false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse4false truefalseS000012219Member_C000033360Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseIrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000033360Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | I17true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:18false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFIXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol19false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse5false truefalseS000012219Member_C000068409Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseR1rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000068409Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | R120true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:21false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFDXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol22false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse6false truefalseS000012219Member_C000068410Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseR2rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000068410Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | R223true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:24false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFEXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol25false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse7false truefalseS000012219Member_C000068411Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseR3rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000068411Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | R326true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:27false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFFXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol28false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse8false truefalseS000012219Member_C000068412Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseR4rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000068412Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | R429true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:30false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFGXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol31false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse9false truefalseS000012219Member_C000117928Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Diversified Income Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000012219Memberdei_LegalEntityAxisexplicitMemberfalsefalseR5rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000117928Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Diversified Income Fund | R532true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:33false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00DIFHXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol34false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse10false truefalseS000024971Member_C000074269Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Global Real Estate Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000024971Memberdei_LegalEntityAxisexplicitMemberfalsefalseArr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000074269Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Global Real Estate Fund | A35true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:36false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MGLAXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol37false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse11false truefalseS000024971Member_C000074272Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Global Real Estate Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000024971Memberdei_LegalEntityAxisexplicitMemberfalsefalseIrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000074272Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Global Real Estate Fund | I38true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:39false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MGLIXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol40false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse12false truefalseS000024971Member_C000117929Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Global Real Estate Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000024971Memberdei_LegalEntityAxisexplicitMemberfalsefalseR5rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000117929Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Global Real Estate Fund | R541true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:42false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MGLRXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol43false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse13false truefalseS000000693Member_C000002006Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseIrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002006Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | I44true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:45false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MGSIXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol46false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse14false truefalseS000000693Member_C000002007Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseArr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002007Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | A47true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:48false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGSXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol49false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse15false truefalseS000000693Member_C000002008Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseR4rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002008Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | R450true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:51false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGJXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol52false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse16false truefalseS000000693Member_C000002012Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseBrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002012Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | B53true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:54false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGBXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol55false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse17false truefalseS000000693Member_C000002013Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseCrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002013Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | C56true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:57false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGDXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol58false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse18false truefalseS000000693Member_C000002015Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseR1rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002015Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | R159true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:60false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGGXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol61false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse19false truefalseS000000693Member_C000002017Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseR2rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002017Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | R262true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:63false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MGVSXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol64false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse20false truefalseS000000693Member_C000002018Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseR3rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000002018Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | R365true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:66false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGHXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol67false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse21false truefalseS000000693Member_C000117927Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS Government Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000000693Memberdei_LegalEntityAxisexplicitMemberfalsefalseR5rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000117927Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS Government Securities Fund | R568true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:69false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00MFGKXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol70false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse22false truefalseS000032712Member_C000100956Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS New Discovery Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000032712Memberdei_LegalEntityAxisexplicitMemberfalsefalseArr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000100956Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS New Discovery Value Fund | A71true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:72false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00NDVAXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol73false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse23false truefalseS000032712Member_C000100957Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS New Discovery Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000032712Memberdei_LegalEntityAxisexplicitMemberfalsefalseBrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000100957Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS New Discovery Value Fund | B74true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:75false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00NDVBXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol76false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse24false truefalseS000032712Member_C000100958Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS New Discovery Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_S000032712Memberdei_LegalEntityAxisexplicitMemberfalsefalseCrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000356349_C000100958Memberrr_ProspectusShareClassAxisexplicitMembernanafalse0MFS New Discovery Value Fund | C77true 1rr_RiskReturnAbstractrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Risk/Return:78false 2dei_TradingSymboldei_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00NDVCXfalsefalsefalsexbrli:normalizedStringItemTypenormalizedstringTrading symbol of an instrument as listed on an exchange.No definition available.false0Trading Symbol79false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse25false truefalseS000032712Member_C000100959Memberhttp://www.sec.gov/CIK0000356349duration2013-02-28T00:00:002013-02-28T00:00:00falsefalseMFS New Discovery Value 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