Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v2.4.1.9
Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
3 Months Ended 6 Months Ended
Nov. 30, 2014
Nov. 30, 2013
Nov. 30, 2014
Nov. 30, 2013
May 31, 2014
Summary Of Significant Accounting Policies [Line Items]          
Net loss $ (4,983,914)us-gaap_NetIncomeLoss $ (3,587,593)us-gaap_NetIncomeLoss $ (8,363,434)us-gaap_NetIncomeLoss $ (6,161,144)us-gaap_NetIncomeLoss  
Accumulated (deficit) (54,797,668)us-gaap_RetainedEarningsAccumulatedDeficit   (54,797,668)us-gaap_RetainedEarningsAccumulatedDeficit   (46,434,232)us-gaap_RetainedEarningsAccumulatedDeficit
Insurance coverage, per depositor at each financial 250,000us-gaap_CashFDICInsuredAmount   250,000us-gaap_CashFDICInsuredAmount   250,000us-gaap_CashFDICInsuredAmount
Balance in excess of federally insured limits 2,127,000us-gaap_CashUninsuredAmount   2,127,000us-gaap_CashUninsuredAmount   4,589,000us-gaap_CashUninsuredAmount
Impairment charges 0us-gaap_ImpairmentOfIntangibleAssetsFinitelived 0us-gaap_ImpairmentOfIntangibleAssetsFinitelived 0us-gaap_ImpairmentOfIntangibleAssetsFinitelived 0us-gaap_ImpairmentOfIntangibleAssetsFinitelived  
Estimated future unvested option forfeitures     0.00%cydy_EstimatedFutureUnvestedOptionForfeitures    
Deferred offering costs 68,292us-gaap_DeferredOfferingCosts   68,292us-gaap_DeferredOfferingCosts   68,292us-gaap_DeferredOfferingCosts
Common stock options and warrants to purchase     23,753,170us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 34,366,833us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount  
Additional common shares if convertible debt is converted to common stock     6,128,333us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities    
Unrecognized benefits 0us-gaap_UnrecognizedTaxBenefits 0us-gaap_UnrecognizedTaxBenefits 0us-gaap_UnrecognizedTaxBenefits 0us-gaap_UnrecognizedTaxBenefits  
Convertible Debt          
Summary Of Significant Accounting Policies [Line Items]          
Face amount of notes $ 5,096,250us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleDebtMember
  $ 5,096,250us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleDebtMember
   
Patents          
Summary Of Significant Accounting Policies [Line Items]          
Amortization period of intangible assets     10 years    
Series B Convertible Preferred Stock          
Summary Of Significant Accounting Policies [Line Items]          
Preferred Stock Shares authorized to be issued 400,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
  400,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
  400,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
Common stock options and warrants to purchase 95,100us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
  95,100us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
  95,100us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
Common shares issued upon conversion of preferred stock     951,000us-gaap_IncrementalCommonSharesAttributableToConversionOfPreferredStock
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
   
Maximum          
Summary Of Significant Accounting Policies [Line Items]          
Preferred Stock Shares authorized to be issued 5,000,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
  5,000,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Income tax examination, year under examination     2013    
Minimum          
Summary Of Significant Accounting Policies [Line Items]          
Income tax examination, year under examination     2011