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v2.4.1.9

Commitments and Contingencies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 9 Months Ended | 12 Months Ended | 0 Months Ended
--- | --- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | May 15, 2014
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Future minimum commitments | $ 660 us-gaap_OperatingLeasesFutureMinimumPaymentsDue |  | $ 64 us-gaap_OperatingLeasesFutureMinimumPaymentsDue |  |  |
Operating lease, rental expense | 104 us-gaap_OperatingLeasesRentExpenseNet | 87 us-gaap_OperatingLeasesRentExpenseNet | 105 us-gaap_OperatingLeasesRentExpenseNet | 129 us-gaap_OperatingLeasesRentExpenseNet | 102 us-gaap_OperatingLeasesRentExpenseNet |
Laboratory Space [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Future minimum commitments |  |  | 0 us-gaap_OperatingLeasesFutureMinimumPaymentsDue / us-gaap_PropertyPlantAndEquipmentByTypeAxis = zfgn_OfficeAndLaboratorySpaceMember |  |  |
Development Based Milestones [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Milestone payments due | 6,700 zfgn_MilestoneLiability / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_DevelopmentBasedMilestonesMember |  |  |  |  |
Pre Commercialization Milestones [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Milestone payments | 12,250 zfgn_MilestonePaymentAmount / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_PreCommercializationMilestonesMember |  | 18,950 zfgn_MilestonePaymentAmount / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_PreCommercializationMilestonesMember |  |  |
Product Commercialization Milestones [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Milestone payments | 12,500 zfgn_MilestonePaymentAmount / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_ProductCommercializationMilestonesMember |  | 12,500 zfgn_MilestonePaymentAmount / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_ProductCommercializationMilestonesMember |  |  |
Subsequent Licensed Product [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Licensing fees per product maximum | $ 1,250 zfgn_LicensingFeesPerProductMaximum / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_SubsequentLicensedProductMember |  | $ 1,250 zfgn_LicensingFeesPerProductMaximum / us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis = zfgn_SubsequentLicensedProductMember |  |  |
Office Two [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Lease expiration date | Jul. 31, 2017 |  |  |  |  |
Lease extension period |  |  |  |  |  | 3 years
Office Space [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Lease expiration date |  |  | Jul. 31, 2014 |  |  |
Lease extension period |  |  | 6 months |  |  |
Office Space [Member] | Before Amendment [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Lease expiration date |  |  | Jul. 31, 2013 |  |  |
Office Space [Member] | After Amendment [Member] |  |  |  |  |  |
Commitment And Contingencies [Line Items] |  |  |  |  |  |
Lease expiration date |  |  | Jan. 31, 2014 |  |  |

X
- Definition Date which lease or group of leases is set to expire, in CCYY-MM-DD format. + References No definition available. + Details
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- Definition Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 + Details
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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717 + Details
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- Details
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- Definition Maximum fee the Company is obligated to pay per licensed product. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of payment due for milestones that have been achieved + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of payment due upon reaching milestone. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Operating Lease Option For Extension Period + References No definition available. + Details
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Namespace Prefix: | zfgn_
Data Type: | xbrli:durationItemType
Balance Type: | na
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- Details
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- Details
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Namespace Prefix: |
Data Type: | na
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- Details
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- Details
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- Details
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Namespace Prefix: |
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Balance Type: |
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- Details
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- Details
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