Business Segment, Geographic Areas and Major Customers - Additional Information (Detail)	3 Months Ended
Mar. 31, 2015 Customer Segment	Mar. 31, 2014 Customer
Segment Reporting [Abstract]
Number of reportable segments	1us-gaap_NumberOfReportableSegments
Number of customers exceeding ten percent of sales	0	0
Percentage of minimum product sales	10.00%htwr_PercentageOfMinimumProductSales	10.00%htwr_PercentageOfMinimumProductSales

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration