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Share-Based Compensation - Additional Information (Detail) (USD $)
0 Months Ended 3 Months Ended 0 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended
Jan. 16, 2015
Mar. 31, 2015
Mar. 31, 2014
Sep. 10, 2004
Aug. 27, 2008
Sep. 17, 2014
Dec. 31, 2014
Aug. 19, 1999
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Share based compensation expense $ 3,000,000us-gaap_AllocatedShareBasedCompensationExpense $ 77,000us-gaap_AllocatedShareBasedCompensationExpense $ 9,000us-gaap_AllocatedShareBasedCompensationExpense          
Issuance of stock option to purchase stock   6,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized            
Common stock reserved for issuance   4,396,233us-gaap_DeferredCompensationArrangementWithIndividualCommonStockReservedForFutureIssuance            
Stock option awards vesting period   2 years            
Unrecognized compensation cost related to bon-vested   70,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized            
Intrinsic value of options exercised             793,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1  
Maximum                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Share-based compensation arrangement by share based payment award options granted contractual term   10 years            
Minimum                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Share-based compensation arrangement by share based payment award options granted contractual term   3 years            
2004 Stock Incentive Plan                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Common stock reserved for issuance       2,500,000us-gaap_DeferredCompensationArrangementWithIndividualCommonStockReservedForFutureIssuance
/ us-gaap_PlanNameAxis
= hdsn_TwoThousandAndFourStockIncentivePlanMember
       
Plan expiration date       Sep. 10, 2014        
2008 Stock Incentive Plan                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Common stock reserved for issuance         3,000,000us-gaap_DeferredCompensationArrangementWithIndividualCommonStockReservedForFutureIssuance
/ us-gaap_PlanNameAxis
= hdsn_TwoThousandAndEightStockIncentivePlanMember
     
Plan expiration date         Aug. 27, 2018      
Share based compensation arrangement by share based payment award percentage of fair market Person holding more then 10% voting stock         110.00%hdsn_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageFromFairMarketPrice
/ us-gaap_PlanNameAxis
= hdsn_TwoThousandAndEightStockIncentivePlanMember
     
2014 Stock Incentive Plan                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Common stock reserved for issuance           3,000,000us-gaap_DeferredCompensationArrangementWithIndividualCommonStockReservedForFutureIssuance
/ us-gaap_PlanNameAxis
= hdsn_TwoThousandAndFourteenStockIncentivePlanMember
   
Plan expiration date           Sep. 17, 2024    
Share based compensation arrangement by share based payment award percentage of fair market Person holding more then 10% voting stock           110.00%hdsn_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageFromFairMarketPrice
/ us-gaap_PlanNameAxis
= hdsn_TwoThousandAndFourteenStockIncentivePlanMember
   
2014 Stock Incentive Plan | Minimum                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Expiration period of option awards           5 years    
Stock Option Plan                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Options granted   70,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
/ us-gaap_PlanNameAxis
= hdsn_StockOptionPlanMember
        1,055,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
/ us-gaap_PlanNameAxis
= hdsn_StockOptionPlanMember
 
2014 Stock Incentive Plan | Maximum                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Expiration period of option awards           10 years    
2008 Stock Incentive Plan | Maximum                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Expiration period of option awards         10 years      
2008 Stock Incentive Plan | Minimum                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Expiration period of option awards         5 years      
1997 Employee Stock Option Plan                
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]                
Common stock reserved for issuance               2,000,000us-gaap_DeferredCompensationArrangementWithIndividualCommonStockReservedForFutureIssuance
/ us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis
= hdsn_StockOptionPlanNineteenNinetySevenMember
Plan expiration date               Jun. 11, 2007