Inventories - Additional Information (Detail) $ in Millions	3 Months Ended
Jun. 30, 2018 USD ($)
Lower Of Cost Or Net Realizable Value Adjustment	$ 34.7
Lower Of Cost Or Net Realizable Value Adjustment Gross	17.1
Airgas [Member]
Lower Of Cost Or Net Realizable Value Adjustment Gross	$ 17.6

Gross Amount of expense related to lower of cost or net realizable value adjustment incurred during the year.

No definition available.

Name:	hdsn_LowerOfCostOrNetRealizableValueAdjustmentGross
Namespace Prefix:	hdsn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration