Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Jun. 23, 2017
Entity Registrant Name	dei_EntityRegistrantName	MAINSTAY FUNDS
Entity Central Index Key	dei_EntityCentralIndexKey	0000787441
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Jun. 23, 2017
Document Effective Date	dei_DocumentEffectiveDate	Jun. 23, 2017
Prospectus Date	rr_ProspectusDate	Mar. 31, 2017
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MASAX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MASBX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSICX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSDIX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSYDX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSIRX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSDJX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSYEX
MainStay Unconstrained Bond Fund (Prospectus Summary) | MainStay Unconstrained Bond Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSYTX
MainStay Government Fund (Prospectus Summary) | MainStay Government Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGVAX
MainStay Government Fund (Prospectus Summary) | MainStay Government Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCSGX
MainStay Government Fund (Prospectus Summary) | MainStay Government Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGVCX
MainStay Government Fund (Prospectus Summary) | MainStay Government Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGOIX
MainStay Government Fund (Prospectus Summary) | MainStay Government Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGVNX
MainStay Government Fund (Prospectus Summary) | MainStay Government Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGVDX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHCAX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MKHCX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MYHCX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHYIX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHYRX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHHIX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class R1
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHHRX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHYSX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHYTX
MainStay High Yield Corporate Bond Fund (Prospectus Summary) | MainStay High Yield Corporate Bond Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHCTX
MainStay Money Market Fund (Prospectus Summary) | MainStay Money Market Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMAXX
MainStay Money Market Fund (Prospectus Summary) | MainStay Money Market Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MKMXX
MainStay Money Market Fund (Prospectus Summary) | MainStay Money Market Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSCXX
MainStay Money Market Fund (Prospectus Summary) | MainStay Money Market Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MKTXX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTBAX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MKTBX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTFCX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MKINX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTBIX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTBDX
MainStay Tax Free Bond Fund (Prospectus Summary) | MainStay Tax Free Bond Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTBTX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCOAX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCSVX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCCVX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCINX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCNVX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCITX
MainStay Convertible Fund (Prospectus Summary) | MainStay Convertible Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCNDX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTRAX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MKTRX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCTRX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTOIX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTINX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTXRX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTXVX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MTODX
MainStay Income Builder Fund (Prospectus Summary) | MainStay Income Builder Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MBITX
MainStay Emerging Markets Debt Fund (Prospectus Summary) | MainStay Emerging Markets Debt Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGHAX
MainStay Emerging Markets Debt Fund (Prospectus Summary) | MainStay Emerging Markets Debt Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGHBX
MainStay Emerging Markets Debt Fund (Prospectus Summary) | MainStay Emerging Markets Debt Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MHYCX
MainStay Emerging Markets Debt Fund (Prospectus Summary) | MainStay Emerging Markets Debt Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGHIX
MainStay Emerging Markets Debt Fund (Prospectus Summary) | MainStay Emerging Markets Debt Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGHHX
MainStay Emerging Markets Debt Fund (Prospectus Summary) | MainStay Emerging Markets Debt Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGHDX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSEAX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINEX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MIECX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSIIX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R1
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MIERX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MIRRX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MIFRX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINNX
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MIFDX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSOAX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MOPBX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGOCX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSOIX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSORX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCSSX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSOSX
MainStay Common Stock Fund (Prospectus Summary) | MainStay Common Stock Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCSDX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLAAX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLABX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLACX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLAIX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class R1
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLRRX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLRTX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLGRX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLINX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLRSX
MainStay Large Cap Growth Fund (Prospectus Summary) | MainStay Large Cap Growth Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MLATX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAPAX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class B
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAPBX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMPCX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MUBFX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class R1
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAPRX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class R2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MPRRX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class R3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMAPX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | INVESTOR CLASS
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MSMIX
MainStay MAP Equity Fund (Prospectus Summary) | MainStay MAP Equity Fund | Class R6
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMPDX