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Prospectus Summary Prospectus Summary S 000002530 [Member] MFS California Municipal Bond Fund MFS California Municipal Bond Fund C 000006978 [Member] Class A Class A C 000006979 [Member] Class B Class B C 000006980 [Member] Class C Class C C 000169767 [Member] Class I Class I C 000194244 [Member] Class R6 Class R6 cik0000751656_BloombergMunicipalBondIndex33Member [Member] Bloomberg Municipal Bond Index Bloomberg Municipal Bond Index S 000002532 Summary4 [Member] Prospectus Summary Prospectus Summary S 000002532 [Member] MFS Georgia Municipal Bond Fund MFS Georgia Municipal Bond Fund C 000006983 [Member] Class A Class A C 000006984 [Member] Class B Class B C 000169768 [Member] Class I Class I C 000194246 [Member] Class R6 Class R6 cik0000751656_BloombergMunicipalBondIndex34Member [Member] Bloomberg Municipal Bond Index Bloomberg Municipal Bond Index S 000002533 Summary5 [Member] Prospectus Summary Prospectus Summary S 000002533 [Member] MFS Maryland Municipal Bond Fund MFS Maryland 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MFS South Carolina Municipal Bond Fund C 000006967 [Member] Class A Class A C 000006968 [Member] Class B Class B C 000169762 [Member] Class I Class I C 000194234 [Member] Class R6 Class R6 cik0000751656_BloombergMunicipalBondIndex315Member [Member] Bloomberg Municipal Bond Index Bloomberg Municipal Bond Index S 000002527 Summary15 [Member] Prospectus Summary Prospectus Summary S 000002527 [Member] MFS Virginia Municipal Bond Fund MFS Virginia Municipal Bond Fund C 000006971 [Member] Class A Class A C 000006972 [Member] Class B Class B C 000006973 [Member] Class C Class C C 000169764 [Member] Class I Class I C 000194238 [Member] Class R6 Class R6 cik0000751656_BloombergMunicipalBondIndex316Member [Member] Bloomberg Municipal Bond Index Bloomberg Municipal Bond Index S 000002528 Summary16 [Member] Prospectus Summary Prospectus Summary S 000002528 [Member] MFS West Virginia Municipal Bond Fund MFS West Virginia Municipal Bond Fund C 000006974 [Member] Class A Class A C 000006975 [Member] 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