v3.26.1
Label Element Value
Risk/Return: oef_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Nov. 30, 2025
Registrant Name dei_EntityRegistrantName MASSACHUSETTS INVESTORS GROWTH STOCK FUND
Entity Central Index Key dei_EntityCentralIndexKey 0000063090
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Mar. 27, 2026
Document Effective Date dei_DocumentEffectiveDate Mar. 30, 2026
Entity Investment Company Type dei_EntityInvCompanyType N-1A
Prospectus Date oef_ProspectusDate Mar. 30, 2026
Massachusetts Investors Growth Stock Fund | Class A  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGFX
Massachusetts Investors Growth Stock Fund | Class B  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGBX
Massachusetts Investors Growth Stock Fund | Class C  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGDX
Massachusetts Investors Growth Stock Fund | Class I  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGTIX
Massachusetts Investors Growth Stock Fund | Class R1  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGMX
Massachusetts Investors Growth Stock Fund | Class R2  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIRGX
Massachusetts Investors Growth Stock Fund | Class R3  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGHX
Massachusetts Investors Growth Stock Fund | Class R4  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGKX
Massachusetts Investors Growth Stock Fund | Class R6  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MIGNX