Decrease in Accretive Value of Preferred Stock Due to Stock Redeemed

No definition available.

Name:	fnjn_DecreaseinAccretiveValueofPreferredStockDuetoStockRedeemed
Namespace Prefix:	fnjn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Decrease in Value of Preferred Stock Due to Stock Redeemed

+ References

No definition available.

+ Details

Name:	fnjn_DecreaseinValueofPreferredStockDuetoStockRedeemed
Namespace Prefix:	fnjn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

License Agreement, Additional License Fees

+ References

No definition available.

+ Details

Name:	fnjn_LicenseAgreementAdditionalLicenseFees
Namespace Prefix:	fnjn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

License Agreement, Fee Receivable Period

+ References

No definition available.

+ Details

Name:	fnjn_LicenseAgreementFeeReceivablePeriod
Namespace Prefix:	fnjn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

License Agreement, Payment Period

+ References

No definition available.

+ Details

Name:	fnjn_LicenseAgreementPaymentPeriod
Namespace Prefix:	fnjn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

License Agreement, Sale of Intangible Asset

+ References

No definition available.

+ Details

Name:	fnjn_LicenseAgreementSaleofIntangibleAsset
Namespace Prefix:	fnjn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Payment For Contractual Obligation

+ References

No definition available.

+ Details

Name:	fnjn_PaymentForContractualObligation
Namespace Prefix:	fnjn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

+ References

No definition available.

+ Details

Name:	us-gaap_ContractualObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Revenue earned during the period relating to consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_LicensesRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of stock bought back by the entity at the exercise price or redemption price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

+ Details

Name:	us-gaap_StockRedeemedOrCalledDuringPeriodShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Equity impact of the value of stock bought back by the entity at the exercise price or redemption price.

+ References

+ Details

Name:	us-gaap_StockRedeemedOrCalledDuringPeriodValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_CounterpartyNameAxis=fnjn_EULicenseeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_LicensingAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_VentureCapitalFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=fnjn_LicenseandSettlementAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=fnjn_SeriesA1PreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events (Details) - USD ($) $ in Millions					12 Months Ended
Subsequent Events (Details) - USD ($) $ in Millions	Feb. 28, 2018	Feb. 23, 2018	Jan. 04, 2018	Apr. 21, 2017	Dec. 31, 2017	Nov. 21, 2013
EU Licensee \| Licensing Agreements
Subsequent Event [Line Items]
License revenue					$ 1.3
Sale of patent in license agreement				$ 4.9
Payment period				10 days
Venture Capital Funds
Subsequent Event [Line Items]
Capital commitment					$ 2.7	$ 5.0
Subsequent Event \| License and Settlement Agreement \| Licensing Agreements
Subsequent Event [Line Items]
Sale of patent in license agreement	$ 65.0
Payment period	20 days
Fee receivable period	4 years
Additional license fees	$ 45.0
Subsequent Event \| Venture Capital Funds
Subsequent Event [Line Items]
Payment for JVP fund		$ 0.5
Capital commitment		$ 2.2
Subsequent Event \| Series A-1 Preferred Stock
Subsequent Event [Line Items]
Value of shares redeemed			$ 6.2
Number of shares redeemed (in shares)			48,076
Reduction in the original recorded value of preferred stock			$ 4.8
Reduction in the accretive value of the preferred stock			$ 1.4