Property, plant, and equipment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 14,230	$ 12,519
Accumulated depreciation & amortization	9,465	9,078
Total	4,765	3,441
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	770	770
Property, plant and equipment, useful life	39 years
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,253	7,312
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Equipment under capital lease
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	231	231
Equipment under capital lease | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Equipment under capital lease | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,212	1,056
Property, plant and equipment, useful life	5 years
Lab and computer equipment, software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,017	903
Lab and computer equipment, software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Lab and computer equipment, software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Furniture & fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	246	233
Furniture & fixtures | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Furniture & fixtures | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	8 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	40	40
Property, plant and equipment, useful life	3 years
Equipment under construction
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 96	$ 609