Label	Element	Value
Prospectus [Line Items]	rr_ProspectusLineItems
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Dec. 31, 2020
Entity Registrant Name	dei_EntityRegistrantName	JOHN HANCOCK VARIABLE INSURANCE TRUST
Entity Central Index Key	dei_EntityCentralIndexKey	0000756913
Entity Inv Company Type	dei_EntityInvCompanyType	N-1A
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Oct. 01, 2021
Document Effective Date	dei_DocumentEffectiveDate	Oct. 01, 2021
Blue Chip Growth Trust
Prospectus [Line Items]	rr_ProspectusLineItems
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund is a non-diversified fund, which means that it may invest in a smaller number of issuers than a diversified fund and may invest more of its assets in the securities of a single issuer.
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Non-diversified risk. Adverse events affecting a particular issuer or group of issuers may magnify losses for non-diversified funds, which may invest a large portion of assets in any one issuer or a small number of issuers.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-diversified risk. Adverse events affecting a particular issuer or group of issuers may magnify losses for non-diversified funds, which may invest a large portion of assets in any one issuer or a small number of issuers.