010000 - Document - Document and Entity Information {Elements} link:presentationLink link:calculationLink link:definitionLink 020102 - Disclosure - Risk/Return Detail Data (MFS Global High Yield Fund) {Elements} link:presentationLink link:calculationLink link:definitionLink 020101 - Schedule - Risk Table {Transposed} link:presentationLink link:calculationLink link:definitionLink 020104 - Disclosure - Risk/Return Detail Data (MFS High Income Fund) {Elements} link:presentationLink link:calculationLink link:definitionLink 020101 - Schedule - Risk Table {Transposed} link:presentationLink link:calculationLink link:definitionLink 020106 - Disclosure - Risk/Return Detail Data (MFS High Yield Pooled Portfolio) {Elements} link:presentationLink link:calculationLink link:definitionLink 020101 - Schedule - Risk Table {Transposed} link:presentationLink link:calculationLink link:definitionLink 020108 - Disclosure - Risk/Return Detail Data (MFS Municipal High Income Fund) {Elements} link:presentationLink link:calculationLink link:definitionLink 020101 - Schedule - Risk Table {Transposed} link:presentationLink link:calculationLink link:definitionLink 010004 - Schedule - Investment Risks {Unlabeled} link:presentationLink link:calculationLink link:definitionLink