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Income Taxes - Additional Information (Detail) (USD $)
3 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Sep. 30, 2014
Income Tax Disclosure [Abstract]      
Percentage of net deferred tax assets recognized due to uncertainty 100.00%sofo_PercentageOfNetDeferredTaxAssetsRecognizedDueToUncertainty    
Goodwill for tax purposes amortization period 15 years    
Deferred tax liability $ 4,283,000us-gaap_DeferredTaxLiabilitiesNoncurrent   $ 4,312,000us-gaap_DeferredTaxLiabilitiesNoncurrent
Accruals of interest and penalties 0us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued   0us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued
Recognized interest or penalties $ 0us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense $ 0us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense