Leasehold improvement liability.

No definition available.

Name:	sofo_LeaseholdImprovementLiability
Namespace Prefix:	sofo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Leasehold improvement unamortized balance.

+ References

No definition available.

+ Details

Name:	sofo_LeaseholdImprovementUnamortizedBalance
Namespace Prefix:	sofo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39896-112707

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=77896938&loc=d3e25383-109308

+ Details

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

- Details

Name:	us-gaap_LeaseArrangementTypeAxis=sofo_Nov2011throughDec2018OfficeSpaceLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseArrangementTypeAxis=sofo_Oct2016throughDec2020OfficeSpaceLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Oct. 31, 2016	Jun. 28, 2011
Long-term Purchase Commitment [Line Items]
Purchase which is not recorded on Company's Balance Sheet	$ 1,200
Leasehold improvement liability				$ 613
Deferred rent credit			$ 130
Nov 2011 through Dec 2018 Office Space Lease
Long-term Purchase Commitment [Line Items]
Unamortized balance of lease	0	$ 7
Oct 2016 through Dec 2020 Office Space Lease
Long-term Purchase Commitment [Line Items]
Unamortized balance of lease	$ 69	$ 75