Average Annual Total Returns - FidelityOTCPortfolio-KPRO - FidelityOTCPortfolio-KPRO - Fidelity OTC Portfolio	Sep. 29, 2023
Fidelity OTC Portfolio - Class K \| Return Before Taxes
Average Annual Return:
Past 1 year	(32.12%)
Past 5 years	11.00%
Past 10 years	16.45%
NS004
Average Annual Return:
Past 1 year	(32.54%)
Past 5 years	9.67%
Past 10 years	14.43%

Return Before Taxes.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection b
-Paragraph 2
-Subparagraph iii
-Clause 1
-Exhibit 2

Name:	rr_AverageAnnualReturnYear01
Namespace Prefix:	rr_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration