Commitments and contingencies - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies [Line Items]
Operating Leases, Rent Expense	$ 830,000us-gaap_LeaseAndRentalExpense	$ 650,000us-gaap_LeaseAndRentalExpense
Remediation Costs Incurred	53,000hdsn_RemediationCostsIncurred	100,000hdsn_RemediationCostsIncurred
Officers' Compensation	288,500us-gaap_OfficersCompensation
Insurance Policy Amount	$ 1,000,000hdsn_InsurancePolicyAmount

Expenditures for salaries of officers. Does not include allocated share-based compensation, pension and post-retirement benefit expense or other labor-related non-salary expense. For commercial and industrial companies, excludes any direct and overhead labor that is included in cost of goods sold.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.4)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Name:	us-gaap_OfficersCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration