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Summary of Significant Accounting Policies - Concentrations of Credit Risk - Additional Information (Detail)
 8 Months Ended 12 Months Ended
Dec. 31, 2014
Apr. 30, 2014
Apr. 30, 2013
Apr. 30, 2012
Summary Of Significant Accounting Policies [Line Items]        
Concentration of credit risk At December 31, 2014, April 30, 2014 and April 30, 2013, no single group or customer represented greater than 5% of total accounts receivable-trade At December 31, 2014, April 30, 2014 and April 30, 2013, no single group or customer represented greater than 5% of total accounts receivable-trade At December 31, 2014, April 30, 2014 and April 30, 2013, no single group or customer represented greater than 5% of total accounts receivable-trade  
Maximum percentage of accounts receivable represented by single group or customer 100.00%us-gaap_ConcentrationRiskPercentage1 100.00%us-gaap_ConcentrationRiskPercentage1 100.00%us-gaap_ConcentrationRiskPercentage1 100.00%us-gaap_ConcentrationRiskPercentage1
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Maximum [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Maximum percentage of accounts receivable represented by single group or customer 5.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 5.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 5.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember