Property, plant and equipment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 14,662	$ 14,230
Accumulated depreciation	10,126	9,465
Total	4,536	4,765
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	535	535
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	830	830
Property, plant and equipment, useful life	39 years
Building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	776	770
Property, plant and equipment, useful life	39 years
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,560	8,253
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Equipment under capital lease
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	137	231
Equipment under capital lease | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Equipment under capital lease | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,258	1,212
Property, plant and equipment, useful life	5 years
Lab and computer equipment, software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,210	2,017
Lab and computer equipment, software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Lab and computer equipment, software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Furniture & fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	249	246
Furniture & fixtures | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	8 years
Furniture & fixtures | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	70	40
Property, plant and equipment, useful life	3 years
Equipment under construction
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 37	$ 96